The art is pretty OK. Some of the fight animation is pretty good, but I don't understand why you would turn all the monsters into similar looking human children. One big problem with this is the editing. It's all over the place. Literally. You show a couple seconds at one place, then cut to another one and we have no idea where we even are. You skip a bunch of stuff like it's not important when we're expecting you to show us more of them, and that can be disorienting. You cut off things that are supposed to happen. You don't show Frisk walking through Papyrus' puzzle and when Frisk gets captured by Undine we're...in Alphys' lab(?). Also, during the Chara fight you break the action axis multiple times. First Chara is on the right, then on the left. Then Chara rushes to the right, only to emerge on that very side. Be more aware of your setting. Also, Chara has no logical reason to attack Frisk, as they are vital to Chara's plan.