I, just like most others reading this manga do symphatize with Michi more than I do with You, he wronged her for a long time and was very unsymphatetic towards her when she was trying to communicate her troubles with him. However, everyone seems to be wishing for Michi to quickly find out about You cheating, as if she didn't do the same thing herself. I agree that to some extent You cheating might feel more unforgivable since his wife was more than willing to sleep with him, and instead he choose to do it willingly with someone else. On the other hand, Michi had an affair that went on for weeks. She cheated both physically and emotionally, even if they didn't go all the way. If I was married to someone and my partner cheated, I would of course leave, but I would be more hurt if he had an ongoing affair than if he had cheated once purely due to sexual desire. Not that I would ever be as bad of a partner as You is though. The only person who I view as being mostly innocent in this is Kaeda, and honestly at this point I symphatize with her the most. Niina should have tried talking to his wife once before he let it go so far as beginning to resent her, he never did unlike Michi.