@MXCL Lemme tell you just how this is goin:
1) You go in puberty, your manga choice now include romance
1a) if you're a boy, you'd be attracted to harem
1b) if you're a girl, shoujo
2) long enough in reading romance manga, you become dull, need more stimulus. Espescially in sexual aspect: ecchi.
3) you began more knowledgeable in sexual aspect, start to think it all 'not giving enough stimuli' anymore. Start the journey of degenerate:
3a) if you're a boy, you start reading hentai
3b) if you're a girl, you start reading smut
4) More "mature" sexual content giving you enough satisfication, for a long time, but at some occasion you start to want more... You search for more "stimulus"... something so deep, dark, that wont even acceptable in your mind at the start...you want to atleast try it. The list of it:
-incest (the same boy meet girl, but with familial connection, giving more exciting "forbidden" & "naughty" feeling)
-yuri
-futanari
-trap yaoi (one of the character is 'girlish'. Even if he isn't. Giving the same satisfication with more 'forbidden' feeling)
-gay yaoi [you are here]
-bdsm
-rape
-pregnant
-guro
-etc