I may be wrong, but Shunji Igarashi doesn't seem to be in this episode (and I was so looking toward to his appearance too). Hiro Mizushima is, but not in as many scenes as I like.
While I had some idea of what I was getting into, I still find some events in Watashitachi no Kyoukasho to be quite disturbing. Apart from the new teacher, practically everyone has issues. Secrets and lies abound. I was watching this with subs and I still don't understand most of these people's bizarre behaviors and motivations. The show also seems a bit soapbox-ish with the question in the title of this post. Despite the soapbox, I could only be glad that it doesn't take an easy way out and agree to one answer to that question.
Hiro Mizushima's character is a math teacher, who, like most on this show, isn't quite normal. But besides being seen in his(?) somewhat darkish room with anime figures filled the shelves and at least one anime poster on the wall (what's the word for this type of person, otaku?), eating chips and typing e-mail message (it did say 'E-mail' in English, but it could have been a chat room or something), his character doesn't seem very fleshed out at the moment. As for Shunji Igarashi, who is the other (slightly bigger) half of my reason for checking out this show, I don't think he even appears in this episode at all. According to the cast list, his character is the vice principal's son.
As I mentioned, I've never really watched any show similar in tone to Kyoukasho, so maybe that is part of the reason I'm not more appreciative of its dark, serious, somewhat depressing and dramatic nature. It may make me sound shallow, but I prefer more light-hearted shows for my entertainment. I do love most of the background music in Kyoukasho, however.
As little as I saw of him, I managed to cap a few pics of Mizushima:
His first introduction, complete with name and occupation:
At a bar, where he is grading students' work (I think):
Also at the same bar, this pic of his sort of reminds me of someone else. (Or maybe it's just my overactive imagination. ;)
End credits pic:
Side Note: I almost didn't recognize Mizushima at first, despite knowing full well he's in this show. (I was certain it was him when he spoke.) I'm just very bad with faces. Seriously, if they only comb their hair differently, let alone have different hair styles like Mizushima does, most of the time I would totally miss them.
Sorry that this is not more positive or much of a review for that matter. Still, opinions do differ and I've seen many praises for this show. So if anyone is curious, or likes dark, serious dramas, please give Watashitachi no Kyoukasho a chance anyway. As for me, I'm still going to continue watching this show, hopefully until it ends.