Inazuma just did the Japanese equivalent of name-dropping PewDiePie.

(Of course, Hikakin's popularity is far smaller compared to PewDiePie and other Youtube giants like Markiplier, but the Japanese Youtube scene is comparatively small in the first place, so this is more like relative cultural equivalence.)

I didn't know at all about Hikanin at first but knew a bit later as I was searching what Akatsuki's presentation from the very first manga page was from (the "Bun Bun Hello Youtube" imitation).