
Nagisa wanted to have sex with Kaito as punishment is probs bc he felt like he tried to take Minato from Kaito by confessing first. He saw himself as a thief that needed punishment bc in his mind Kaito is so amazing that Minato will definitely fall in love with him. So, he wanted to sleep with Kaito as a substitute for Minato or as loveless/painful sex bc unconsciously he has always loved Kaito and wanted to sleep with him. So, by having sex with Kaito who doesn’t love him and would only be doing it out of revenge, he will hurt himself deeply since he’s in love with Kaito. He also did feel like Minato dying was his fault due to Kaito’s words so that was another reason he felt he owed Kaito.
And I think him sleeping with random men was also self punishment. For him it meant he would never sleep with the one he loves since he felt he didn’t deserve happiness. Although this was all unconscious thoughts and actions since he wasn’t aware he love Kaito and wanted to be Minato who he saw as equally as great at Kaito. Minato was his god, the perfect version of himself he wished he could be who would match well with Kaito.
Not perfect but also not as bad as some people make it out to be. Artist are people with extreme emotions and so are their muses. So it seems overly dramatic at times because typically artist feel emotions at a pretty intense level and for most ppl that’s a lot.
Also, Michiru does have character development because he choses MC on his own and wanted to experience love for himself. He also ruined the tattoo because he no longer wanted to be sensei’s art. His new tattoo is a collab with MC bc his self inflicted scars are the base (the roots and stems of the flowers) for the whole tattoo. MC even says this and Michiru also helps MC get recognition for his work and pushes him to NY even if that meant he would be alone. Those are all choices he made on his own.
Additionally, he’s encouraged by MC to attend Uni and MC teaches him English. It’s odd to say he has no development when he clearly started to think as an individual and got a BF all on his own with like zero life skills.
Before MC he legit did and acted in the way sensei told him to. He was an add on to sensei’s art, a breathing statue that has 1 request in his entire time with sensei, to get MC’s painting from years before.
Anyway, happy he has a chance to get educated and build a career for himself. Maybe as a model or something.