To answer Shoujo Q's question about what's math rock, they call it math rock primarily because the time signature (meter) of the songs tends to be exotic and to vary a lot, so instead of traditional 4/4 music you'll get stuff like 13/8, but I think also because of the discordant layered guitar sound which has a lot of complex chords like 9ths and 11ths. It usually features long, moody instrumental breaks and has a sort of wistful quality. Here's a nice selection:
I guess another reason why they call it math rock is because it's not really danceable, and the artists often embrace a kind of nerd/galaxy brain aesthetic. JYOCHO's "Sugoi Kawaii" MV puts that on display.
Out of that whole playlist, probably what stands out to me most as a classic J-math-rock sound is the medley 8films/tobira, by Uchuu Konbini, so here it is by itself. Nice video.
It even got covered by a Russian group. Like the drummer writes in her YT post, "Japanese music is so varied, interesting and amazing that it's difficult to resist." Facts.