The true ending is likely either in 3-C where you accept mark and lark then get the unique passive the black star, I assume its not fully implemented yeti already read that guide thats how I knew to get those two. It doesn't say anything about an ending after that though so unless that in of self is the ending which is honestly isn't an ending just a cliff hanger.
or in a separate future ending where we actually manage to unlock the mirror and meet with gf, this seems to be the biggest motivation of the mc Pre amnesia