First, there’s the point that several people have picked up on and which I’ve talked about in my previous post: Riki is surprisingly negative. If you do something he doesn’t understand, chances are, he’ll assume you have ulterior motives or downright bad intentions. As another example, you can cancel the progression to Rin route during common route when Rin gets the “perform a riposte” mission. If you do, Riki explains this decision by assuming that the sender of the letters is using Rin for his own amusement!
There’s also the part where he can behave calmly and naturally around girls and girls, in turn, drop his guard around him since they don’t consider him a threat. But we’ve already been there.
Another point is that Riki is, to my mind, the protagonist with the most “heart” among all Key protagonists, because even by a protagonist’s standards, the dedication he shows to his friends and lovers is enormous. Admittedly, we don’t really see that part of him just yet in the common route.
However, he is not your typical nice guy, even though he totally seems to be one. No, this does not contradict the previous point. Let me explain:
Many protagonists, especially those from harem settings, are just nice guys by nature. Riki, however, does nice things - despite being negative - for a certain reason. That reason is most obvious in the Mio events of the common route. Riki sees Mio all alone and isolated and wishes to pull her into his group of friends, like Kyousuke did for him when he was suffering. In other words, Riki is being nice because he knows from experience that kindness can save people.
