I guess I didn't use my brain enough when considering bullet avoiding.
The bullets stopping out of view can do this: https://imgur.com/E7KRrdA
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That is indeed a problem I did not consider. The intended solution for avoiding Koishi's bullets was to get on the elevated part behind which she spawns fast enough, so that you can safely wait for them to pass by while Satori doesn't hit you due to being blocked one tile to the right on the upper part.
A big advantage of a team seems to be simply having a playtester who doesn't know what the programmer intended to happen.