Thanks Daphie!
Masashi is a child, I mean really a child. Even adults find it hard to think from someone elses point of view or understand they have problems that are affecting them. So expecting him to understand an adult is asking a bit much. I wouldn't say he is in love with her, or even that he idolizes her. To him she is the sun and the moon, an angel. When he realizes she is a real person with all of a persons flaws, or when she in some way rejects his love or worship for him it will hurt, a lot.
As an adult I think he is trying to discover who she really was, to make the angel real, to fall in love with the real Asa-nee. Or at least come to terms with the absence of her in his life. When your a kid and you fall really hard, really fast for someone, it can leave a lasting impression on you for decades.
As for him being happy that Miki didn't hurt her, I think it had more to do with him not being there to protect her. If Asa-nee hurt herself in some way that is one thing. But if someone maliciously attacks your loved one and you failed to prevent it, it would bother you quite a bit. Especially if your a young boy. Though not knowing any Japanese I have no clue if I'm right or not.
I didn't even think Miki's story reminded Asa-nee of her past. I was just thinking she was empathizing with Miki. Asa-nee seems to be a very compassionate person helping the kids with their problems. It seems like all the kids have issues but the abuse Miki has suffered is on a whole other level. She needs some serious help.
I know I said I hope he and Asako somehow end up together at the end but this chapter made me really feel for his childhood friend. A contest between the childhood friend and the onee-san. My two favorite archetypes. I hate when that happens.