Trying to understand each of the guys
Tai-chan
We see Tai-chan express affection to Ruru from the get-go during the first group cooking session, but redirects his interest to Hikaru when the elder Leo also expresses in her. Being the youngest male of the group, east Asian customs would have it that the younger person will give the way to the older, especially if they're not close. But when Kazuma came in and started openly pursuing Ruru, it was open warfare and Tai-chan felt justified to also pursue his true desire.
Ari
Deeply emotional, sensitive artist. A poignant man who shouts wassup as armor for his tender heart. What can you say about a boy who falls in love at first sight? Unrelenting foolishness, overflowing with youthful energy, he was prepared to do anything to convince Hikaru.
Leo
Man fumbled. He has a cute, kind of perverted side which at times complements his manly, resolute nature. But when Kazuma came in like a storm, he wasn't able to recover and Ruru stopped seeing his playful side. Just rock solid, "I haven't changed." Personally, I think he should've lightly poked fun at Kazuma's playboy character and more explicitly demonstrated hat he can take care of her, build stability, have a family, and live a happy life with Ruru. He's only 25 though, still has time.
Kazuma
Outside of the obvious, wasn't he surprisingly intelligent and sensible? Especially in the interviews. I guess you still have be pretty 'in touch' to know in which way to deck yourself out and fashion the best version of yourself (except the teeth wtf).
Bo
Honestly just happy for him because he emotionally processed so much of his troubled past actions.
Ma-kun
Physically, kinda elite. Must've had an aura to him when he moved, especially since he is a martial artist. But emotionally, kinda frustrating. Conflict avoidant and subservient to the alpha of the group. Felt so sorry for him when Assun kept acting so immature.