He doesn't really have to accept polyamory seeing that Luca hasn't been looking at anyone else, polyamory is just Luca's preference but that doesn't mean he can't be with only Makoto.
Makoto didn't experience any negative emotions towards Luca's preference either, jealousy can be a part of polyamory too and a healthy part if there is communication like this couple has.
At best I feel for Luca cause he has to accept monogamy to stay with only Makoto but most people only think of one side haha
Just because Luca isnt currently dating multiple people doesn’t mean he never will/want to.
Just because Makoto didn’t react negatively to Luca’s preference doesn’t mean he wants it for himself. The poor thing thought he was being narrow minded. Makoto shouldn’t be made to feel bad because he isn’t into polyamory.
Someone would have to make a concession. That’s normal in relationships. If Luca likes Makoto and exclusively wants to be with him, there should be no reason to feel bad.
This is a manga so I think we can all agree that polyamory is most likely not going to happen, that means that you only sense danger because he's poly, all of these points would've made sense if this was real life.
And I agree Makoto shouldn't feel bad, but the seme is not making that happen. If Makoto feels bad it's because he himself is jealous of relations that his seme doesn't (and probably will never) have. Again, you sensing danger signals from the seme despite that fact that he has done nothing and is literally just poly.
Lastly, if Makoto likes Luca and wants to be with him, he should be able to understand that he prefers polyamory, just like how Luca can do it vice versa. The point is the seme doesn't have to be the one bending or giving "danger signals" because he's poly.
..... 3rd chap doesn't feel right... Kinda sus..didn't like it. I'm sensing a danger signal coming from seme. First 2 were literally so wholesome! So cute!