right? i mean there should be some trigger point or something kind of event like scene explaining why he will do it.
Instead of that he goes to his room and plug a dildo his in ass which is he never considered before.
Onori's relationship level 5 event was all about ramping things up beyond what Riko felt he was prepared for (he offers to give her a handjob if she digs him out of the sand, but she replies by asking why she should settle for a handjob when she can already get him to give her a blowjob right now). And then after the scene she shamelessly gropes Riko's butt before they go home. I think Riko is smart enough to get the idea that things will soon escalate to buttstuff if he keeps hanging around Onori.
I wouldn't be surprised if the relationship level 5 events for Yui and Eri will also have
some element of teasing the idea that soon they will be playing with Riko's butt. I could see Yui's scene being something like Riko offering to be her masturbation aid and posing for her when she starts feeling too pent up, and then she jacking off to his naked butt (less embarassing if they don't have to face each other) or even going as far as rubbing it against his ass and cumming on it if she starts losing control. No idea on Eri yet though, need to see how things go in her relationship level 4 event first.
Also it is not like he went to his room and immediately shoved the dildo up his ass, he first played with it a bit reliving some of what he already did with Yui and Onori (stroking it, putting it in his mouth) but felt it was a bit underwhelming compared to the real thing, and then the lustful self sneaked the idea into his mind that he should try using the dildo for what it was "primarily designed for" before being done with it. Riko was then extremely flustered but obviously aroused at the idea, tried to deny it by saying he would totally
never do such a thing, and then 1 transition later he was already getting ready to try to do it. Classic comedy gag.
All this to say that in my opinion it is not like Riko getting the idea to play with his butt came out of nowhere, it was already on his mind and his naughty side couldn't pass on it once a perfect opportunity landed on his lap
To trigger the events we are grinding this game for breakpoints of each characters, There should be some kind of breakpoint for MC too, for which we players can find it understandable. We all know that he will become a fleshlight femboy for entire family at the end or middle of the game, atleast the flow of story and character should needs to be balanced.
I do agree with this though. This was very much a Riko scene, not really a Suzuki one. I think that for story progression it is important that this scene can only happen after the conversation with Suzuki, but it would be interesting if the final trigger condition was more personally related to something Riko is doing himself (either having gotten enough level ups on his selves, or spending a big amount of "self-reflection" points to make himself open and prepared for a "big new experience").