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Niiyama Niko seems to be a character that's inspired by Kill la Kill's Mankanshoku Mako (behavior) and Harime Nui (appearance).
Tenga Hajime seems to be a dumber version of Kamina from Tengen Toppa Gurren Lagann. Are there any other referances/homages to be found in Kiznaiver? For example, maybe something from Little Witch Academia?
FYI: Kill la Kill, Kiznaiver, and Little Witch Academia are produced by Trigger, which was founded by members of Gainax, which produced Tengen Toppa Gurren Lagann.
Mako: the gif I actually wanted to post