I haven't read the prequel, so I have no idea what that's about, but I must say that I love Reiichirou, he's not perfect. Far from it. He's too blunt, too naive, too clueless, too unobservant, in fact, he's a whole list of too many other things that it'll take me ages to put everything down. Too pretty for one, it's enough to make a girl jealous. But that said, he's also very, terribly endearing, that's in my opinion anyway.
I like his personality quirks, I like that's he's truthful and sincere about everything, it's rather rare in this day and age. I can even extend my favour to his stupid innocence as well, it makes him rather refreshing coupled with that tactless wit of his. In all accounts, he's probably not the usual uke, he's not bright, cheerful and child-like, neither is he stand-offish and stubborn and energetic, and he's not sweet and demure either. So in some ways, his personality might not be for general consumption, but for a select group of people with particular tastes, which well, clearly includes me.
As for Jinnai, he's more typical; domineering, strong alpha male type, but not quite manipulative. He's the lighter type of seme in my opinion, think Hasunobe from Bitter by Minami Haruka, not Asami in the Finder series by Yamane Ayano. The problem with the generally good seme Jinnai is, is the fact that he's insecure.
Of course, one might find that sweet and lovely, but in my book, semes are to uphold the rules in How To Be An Alpha Male 101, and be absolutely confident in their fatal charms. So this is clearly about preferences, I happen to favour scheming, manipulative semes like Asami (of course, I do still like the lighter semes), but another person may enjoy the gentle, understanding semes. In any case, this series would still come highly reccomended by myself, and on another note, I do believe I dislike Tsukasa.