It's disgusting how people seem to think that a high-schooler considering himself too imature for sex is a "miss", like mf they're KIDS FFS, there's a reason why even a french kiss was a whole ass drama before, also considering his personality, he probably takes every single possible and imaginable risk into consideration, and that includes the risk of pregnancy, witch, as was show by the story of the mother of the girl this chapter is centered around, can completely derail their entire lives. Unless you're living in hentai-land, high-schoolers being active is IMPULSIVE and RISKY, and all around a bad decision. And i say that from experience of seeing two cousins dropping from high-school because the stupid bimbos couldn't keep their legs closed and got pregnant.
Also, this.
By the time Chyio is 18, him and most of the cast will be 21, and Hahari, the oldest one other than Yaku, will be 35, THEN things can move in that direction.