( slight tw )
Keep in mind that when smut is written, think about the laws of the country it would be written in before complaining. If a teenaged person is writing smut about fictional teens in japan then they literally just have to be 13 years old. Writing smut for 13 year olds is weird yes but for 16 year old fiction characters it's not that uncommon. We cannot stop adults from reading what we write, and usually, if I'm not mistaken, most adults wouldnt read smut anyways and if they did they probably read aged up smut, and before you say, it's not the same thing. They were purposely made fo be older in that scenario and often times do resemble the character, obviously but look much older than in the anime. Also they're FICTIONAL characters.
I would rather someone read about people way younger than them doing indecent stuff then seeing that someone got harmed in real life.
Let people enjoy writing please.