The main character is looking at the window of his room and he sees something(he's drunk).
My conjecture is, someone is doing something to his wife because he says he couldn't even do anything about it. But what confuses me is, why does he say, "there were two small animals" (first bold text) and then says 「これもまた人間の姿だ」. Is he assuming that what he believes to be two small animals are in fact two people and his wife is cheating on him ?
Further down he says
Which seems to indicate that he believes his wife was violated and he reads novels about wives cheating on their husbands but her way of cheating was unparalleled ? But it doesn't seem to fit somehow. I think the above sentence might also mean, she was the victim and he is searching novels for ways to deal with it. But the former assumption (of her cheating) seems to have a supporting context further down
Above sentence talks about the main character's feeling about the husbands in the stories but he then supplements that with his own thoughts about the matter with her wife which makes me think she did something that asks for an apology to the main character.
Sorry for the long winded question. Here's the entire context: http://dazai.or.jp/modules/novel/index.php?op=viewarticle&artid=158&page=56