After many runs dying at the very end I finally clutched this amazing run! I've now beaten the previous Umihara Kawase video record which was by Guterham with the time of 21.75. There's actually an even faster time with normal Umihara Kawase by 天原 with 21.60 on Steam (or 21.58 on PS Vita, but I can't confirm which character was used), however no videos of these runs exists. For reference the real record stands at 21.51 by グロいうさぎ but with the use of Noko's Time Stop Ability.

But yeah, improving this time will take quite some grinding I suspect, so we'll see if I can keep pushing my time lower in the future.