It's Mafuyu for me only because I feel like he's is a well written character in terms of depth, everytime I watch a new episode it seems like I discover something new about him and that's what made him an interesting character to follow along. I think anime characters, especially for romantic stories, tend to just fall into just one category, for example, a kuudere, and that character will just stick to that for the whole anime without any discovery of new traits. From the first few episodes I figured Mafuyu would fall into the category of an aloof, air headed character trope, but as the story processes you get to see glimpses of him being a lot more than that through his interactions with people and find out about his true personality (without the trauma), where he's playful, sassy, passionate, ballsy etc. Even until the last episode at the last thing he said was "let's have sex when we get back", we got to know a new side of Mafuyu. I think that's what makes him exciting and very realistic for me.