eh...
Ok I can really tell why is this is being called Hentai.... One can only assume what happens three minutes later after that french-kiss , and apperant hogging of body. And you may say 'you have perverted minds' but you ARE portraying a french-kiss and it's really heading that direction.
Also, besides of the point of the two characters being lesbians, THEY DO NOT LOOK like adults; it looks like a 13y/o girl french-kissing a 16 year old girl, and that to me, disgusts me (the second half of it). It's portraying animated children almost... egh.. I'll stop there.
Dun get me wrong, I love your style and graphics, but you might want to portray them better and more specifcly next time.
Also specify who the letter is for; I wouldn't send this to a female friend, with me being a guy and her being straight.
There, constructive.