Calm down. It's okay. Just fiction
Allowing such things to go on, even though it’s fiction, creates a narrative that makes it seem acceptable, even in the real world, which makes it problematic..
I don’t see a problem with the age gap. He is in his last semester in high school so he is probably 17 and very nearly 18. And the older guy is only 25. I myself was 19 when I started dating my husband and he was 27. We have been married 14 years now. As long as the intimacy waits till he turns 18 then it’s fine.
Hope they get seperated and then reunited when he’s older, ‘cause a teenager with a 25 year old..(⊙…⊙ )