One thing I’ve noticed much more with the TV version of Sakamoto desu ga? than the manga is that there’s just not a lot of in-between with this series. It’s either going for full-on comedy or it’s quite serious and dark, and as you know by now it has a decidedly disturbed side when it decides to show it. It’s clear now that the anime version is going to end with a pretty serious arc (the original final episode won’t be released until October 26 on Blu-ray, due to the Kumamoto earthquake delaying the TV airings by a week), though whether it’s going to reflect the manga end I’m not certain.
Katase-san is at the root of this series’ darkest threads (though I’d argue Kubota’s mom its most disturbing ones), but it’s through Acchan rather than directly that Katase is driving this arc. When a snowstorm hits (they are indeed rare in Japan’s major cities outside of Hokkaido and Touhaku) Sakamoto casually mentions to Acchan that he’s never seen snow on the ground before (the hints just keep dropping like anvils). Acchan sees this as an opportunity to school Sakamoto-kun on how to play in the snow, though the results are predictable (the best comedic moment of the episode comes when Acchan’s sideman notes that the snow angel Sakamoto makes looks like the anatomical model drawn by “Leonardo DiCaprio”).
Acchan was really the first domino to fall when it comes to the bullies being won over by Sakamoto, so to see him staring into the heart of darkness here at the end is a bit surprising. I guess when confronted by someone as coolest as Sakamoto one can either do what Kubota and the girls do and become worshipers, or resent it. Acchan seemed to be in the first group – clearly he has to fight down that side of himself – but personally I think I’d find being one-upped by somebody pretty annoying, so I don’t blame Acchan for secretly harboring a grudge.
Katase seems to be Sakamoto-kun’s dark analog – I doubt the thing about him being reborn a million times, but it wouldn’t surprise me if he were indeed a genius simply sticking around high school because torturing kids amuses him. Katase always uses others rather than engage his perceived enemy himself, and Acchan is the perfect surrogate. Katase comes off as a genuinely sinister figure, especially for a comedy. Whatever secrets are uncovered about Sakamoto’s personal history, it wouldn’t surprise me if Katase is somehow connected to them. As for Acchan, I’m pretty sure Sakamoto will save him from the dark side in the end.