Wow I like this game xD

where is Help section? options? pause? why I can't change difficulty after I was defeated?
and please don't say I should search Help section from this game in another game

I'll try to segment the review into pieces so it doesn't end up as one giant ramble- but mainly the thing that needs improving across the board are the various design choices I've seen in this one.
Graphics:

The player and assistant have good, serviceable animations. The cat heads got a little bit tiring after a while, but their explosions didn't claim the screen if they happened at all and the vehicle enemies blended into the background almost a little too well. As a design choice, the confirmation of dealing damage needs to be much more apparent. I wasn't aware the turrets on the U-Haul needed killing because my weapon of choice was the giant doom laser and it completely obfuscated the method you do use of turning things grey because they were so small. Eventually I coated the entire vehicle and *something* blew up to finally clue me in. The spellcards used to change weapons are way too small for the UI at the default resolution, especially in that they're also sometimes flashing. Making enemies flash more explicitly every now and then when you hit them can go a long way towards reinforcing the concept that the player is dealing damage, which is how you want them to feel. Why did the walker miniboss not have a lifebar?

Audio:
I can't complain about the audio at all. The music wasn't too grating, and the sound effects were very concise and well used. The sounds for each weapon fit very well, the only little thing thing I'd maybe say is that the initial gun is a bit too loud- did you use a pre-constructed noise that so happened to be a bit louder than most things?

Enemy Difficulty:
The enemies wobble between completely worthless (spear angels) and super high priority (tanks from behind.) The dominant strategy becomes to camp the road so that you have a constant clear line to kill the ground based tanks before they fill the sky with unavoidable death that you cannot retaliate against because you can't fire vertically. Those enemies are cool and all but they totally dominate the gameplay. It became about literally dodging bad weapons once I got used to it.

Character:
What is my hitbox? I still don't understand it. I mean, whatever it is, it's very generous. I dodged a lot of shots by taking a chance and using my literal sprite graphic as a reference but I feel like it should be explained in the tutorial you're going to put in the next one (like you did in the first one) exactly what your hitbox is, and what the damage box is on the varying weapons because at least one of them (The giant non moving laser of terrible) felt a bit deceptive. If my hitbox is my actual graphic, that's amazing. Do me a solid and point that out though, I'm more liable to think it's a square because that's how bounding boxes work.
How does my reactor work again? I blow up when I shoot when it's overloaded? I remember several instances of doing that just fine. If I hold the laser down and go INTO overheat, it doesn't kill me. If there's a "you die here" line, mark it clearly on the reactor. I can't see the line after it charges to a point! Was that a design decision, that as I take damage I get a bigger window to deal more damage at the cost of actually dying if hit or if I go over the max? I'm just not gonna fire at all.
If I get attacked for lethal damage, an overheat countdown begins where I can fire as much as I want- this is a desperation ability, except that it's useless unless you end the game/level in that state right? Anything I kill in that state has a chance of dropping something I want, which I won't be able to pick up after I've finally exploded. It's a bit silly. Can I just die faster instead?

Weapons:
So this is the most important part of any shooter- what you're shooting with, and to be honest most of the weapons were pretty crap compared to the giant laser although to their credit they weren't all bad.

Standard pew pew pew weapon "Break Sun"- It's very small and has a travel time, it's only advantage is that you can safely hold it down. If you attempt to use this to engage enemies from two sides, you will be quickly overrun.

Pretty OK "Hell Wave cannon"- This one's actually not that bad- quadshot is good. It kills multiple things, such as multiplying cat heads. It's reactor rate is good. It's simply overshadowed by the giant laser, but it's honestly not a bad weapon because unlike it's friend the shooting star it's a *controlled* way to fire in a direction that isn't directly horizontal. Good for advanced play if you like the concept of not literally camping the road all day.

Bosses are gonna be a problem "Shooting Star"- This one isn't too bad either. The rapid fire rate and natural dispersal mean it tends to carpet bomb whatever you hold it down at. The problem arises in boss encounters, where you need to stay away to avoid instant collision attacks and the spread becomes instead a huge liability. I don't really want to fight bosses for 10 more minutes than I have to because I need to kiss them to make this hit properly.

The best "Radiant Blade"- This is hands down the most powerful weapon. It has no travel time, which means instant response no matter what you're doing at the time. It has infinite piercing, which is awesome and broken. It does so much damage even at level 1 that you can literally hold it down and "scrape" the battlefield clean. If you have decent overheat rating, it deals really good boss damage as well- and it's super accurate because the laser of course is relative to your own position. Even when you get low on reactor, just tap the button a lot and you have a decent weapon still.

In contrast, the worst "Hell Geyser"- This is radiant blade if it were implemented badly. Instead of, you know, a projectile weapon, you instead have what I can only compare to a battering ram. It takes more than *instantly* to kill things with this, which is often lethal. You can't affect anything coming in from offscreen unless you're there, which means you're not affecting something on the other side of the map. Oftentimes you unload and kill maybe one set of cat heads, only to have to move anyway because you took so long that you had to fall back as you did so- which means you had to reposition again, which means you don't get a good angle on the next thing, which means you can't kill that, which means it fires at you, which means you dodge- ad infinitum until an enemy drops something better. Or even better, you hit something and then instantly overheat. Yay, I got punished for killing enemies with my not-gun!

Uh ok "Melt Wave"- This was an interesting concept, and very syntactically well executed, but generally when I fire at something in a game like touhou I want it to take damage. Am I supposed to be setting traps ahead of time in randomly generated levels? In order to keep a shot prepared, you have to hold the button down- which makes you fire more, which increases reactor, which means you have to release eventually. So why not just release right away to begin with? And then it turns into a gun that you fire by mashing the button instead, which reminds me of chocolate milk in Issac except worse.
It was REALLY COOL though. Melt Wave 100% wins the "most style" award.

Deceptively good "Shooting Sun"- This one isn't bad, mainly because of the exploding shrapnel. It becomes a good way to kill catheads, but not a good way to kill tanks or bosses. At least it's strictly better than the initial weapon.

If I named a weapon that was only in the first one and not in this one then forgive me, all those cards look alike.

UI:
I feel like you should look into increasing the resolution of the game window so that you can create more expansive levels with more varied enemies. Everything is cramped and it's very easy to just get ganged up on unless you have a good weapon. A lot of the enemy attacks blend into the background too well- even though they use contrasting colors, they're simply too small to convey meaningfully until it's too late and that's a function of the size of your game window. That can't be the max, that's unfair if it is. I've seen games with a larger play window. Look to RaidenX and all it's spinoffs, an older entry, for clues as to how to convey bullets and powerups in a very clear fashion and notice how they straight up dominate the screen. They have super small play screens, yet it's very easy to tell exactly what's happening. The pre-rendered backgrounds are nice and all but in the end what's going to matter is my ability to play the game and I can't do that hunched over and squinting at my monitor. Yet at the same time, this is a huge step up from the first one where there WAS no background.

A lot of the powerups look very similar to each other and it's aggravating to miss them because I exploded something midscreen and instinctively dodged away from a bullet only to see a powerup I'm never going to catch up to float away. Penalizing me for killing enemies by presenting weapons I don't want that will override my weapon of choice feels like bad a gameplay decision that could be solved with (anything!) something as simple as a weapon cycling key using Q and E or as expansive as zxcvbSpace or 12345qe. And with some of the weapons that's what it is- a penalty! I feel like if I accidentally pick up Hell Geyser I should just reset because I'm going to eat infinite damage getting a level 1 weapon back where I could just reset and have something better in the end. If that's going to be the case, give me a reset button. Or if I have a fully charged doomlaser and I get ANYTHING else, it's GG. I straight up avoided everything once I had that bad boy. Or even better, give me a weapon ejection button or something so I can choose to rid myself of something I didn't want in the first place. Have it remember the previous weapon for newbies, so they can get a test drive or something and then eject it if they don't like it instead of sticking their lack of knowledge to them for the entire run before their eventual death. Limit me to two weapons and let me cycle between those and override the one I have out so that I can at least have the skill test of changing weapons before I collide into a bad powerup or something- that would be cool. I realize the exact entry I mentioned before, RaidenX, did this as well but we're in the modern era now and we can choose to not make those choices in the interest of fun gameplay instead of sucking quarters out of people ^.^.

The A.I. companion was basically worthless. I'm sorry, but she's way too dumb for her own good. She keeps disobeying my order to "Get over here" by deciding to fly in and kick whatever's nearby which changes her position because she then decides to stay there. I stopped caring after a while because my job isn't to keep her alive by going where I think no bullets will EVER go and mash down, my job is to kill everything on the screen. She's not good at dodging unless you macro your keyboard to mash down rapidly enough that it's pointless because it broke the entire point of her. Her damage and HP was passable, usually dying at the walker boss, and I really couldn't be bothered keeping her on the field. What if she were a timed invincible powerup instead? That would feel a lot more impactful and I wouldn't have to mother hen her all the time.

At what I assume was the end boss (Maid girl with knives) I triggered a bomb in self defense during a multi-knife throw and after it cleared all the projectiles my game violently froze up with a repeating sound file of whatever she was saying in Japanese as if it was constantly running a loop and that's when I stopped playing, but that doesn't mean I won't play the next one if and when it comes out. I've finally found a shooter since Wings of Ge.ne.sis. that kept my interest. Yay!

it had lag at the start. kept going too. great game, but a bit laggy. think there is a way to fix it?

Strangely... I found the first one better. Maybe it's just me but with Reimu, the game became blurred, and we can't see the bullet coming. BUT it is a very good game, with an excellent gameplay, etc (I'll just say the same thing that yesterday ^^)
I think that the background handicap the vision of the bullets, so I'll hope that you'll fix that :P
Aniway, very good game, so good luck for the next chapter!

PS: I congratulate you from France!