Mika-chan is Raphael's best friend, even when both are very different. They argue a lot but it is no real dispute, it is because they are both the opposite of the other (and because Michael is the war-angel ^.-). Michael is the angel of fire and war, and also Lucifer's twin. Lucifer is Michael's weak point, that's why Raphael kept all the gossip away from Mika. Even when they don't show it, both couldn't imagine a life wihout the other. Raphael is always there for Mika, as well as Michael is there for him. Raphael always holds Mika back when he comes in a bad temper and wants to burn everything in his nearness down. When Michael heard that Raphael knew it all the time with Lucifer and the sword Nanatsusaya, that he was sealed in it etc, he was so angry at him. He shouted and didn't even punch him (Michael does this sometimes, but I think, here he was even too anry for this) and flew away. Raphael looked sad after him 'I just didn't want to see you falling apart again. Right befoe my eyes. Like you did that time...' I understand both, Raphael and Michael. Michael is angry with him because he didn't told him the truth. Raphael didn't want to hurt him. It's a really complicated situation. But then Michael remembered. Raphael gave him courage when he was so angry about Lucifer and coulnd't control his power anymore. No one helped him, all looked at him, burning, and were frightened. But then Raphael came and he went towards him all alone. Michale said no, he shouldn't come any closer or he will hurt him. But Raphael put his hand on Mika's head and said 'Oh come now, Mika-chan' and cheered him up to believe that he would have won the fight against Lucifer if Bal woulnd't have rescued him. Raphael told him that he should become stronger and to make sure he never forget his resolve, because it is just the beginning. Michael shouted at him, he should heal his burns but Raphael just smiled (!! HE SMILES! He does this so rarely...), put out a cigarette and asked Mika to light it. But also Michael helped Raphael very much before this. It was just after the thing (see Past) with Belial, when Raphael was isolated from society and very sad. But Michael cheered him up, make Raphael come back to his life and from his desolation. Raphael thinks Michael is somehow invincible, he is the only one who hasn't changed all the years and only Lucifer could make him.
Michael also makes him relaize that Sara doesn't belong to him, only to Setsuna. Raphael explained why he acted this way, locking her in and so on. He wanted to seduce Sara, but her 'Setsuna! Setuna!' just didn't stopped. After Setsuna&Co left, Michael says to him 'Come on, come with me.' When Michael finds out that Raphael has to recover for ten years, he said that he will wait for him to finish their fight. Mika says he was a fool to be so short tempered. Even when he shows Raphael his middle finger, Mika is sorry for fighting him. I think he also wants to say sorry and I like you.. well.. that's just the way Michael is. Maybe Mika would act a little bit different when Barbiel weren't also in he room.