We know that she began as a truly terrible person. We know that in one loop she murders everyone in order to corner her former victim. We know that in another loop she manages to transfer her consciousness out of cold sleep to destroy the crew. We also know she became friends with Otome, and that the world with no Gnosia was almost certainly not her last loop.

But we don't know in what order she looped. We don't know if guard duty with Remnan was her first loop or her last, if the Gnosia incident occurred before or after she went to Nada with Otome. Kukrushka is a black box of a character; we don't know if she cares about Jonas and Stella, how she felt about SQ, what she feels at any given moment, what her priorities are. At no point did Kukrushka attempt to talk to the player or Setsu despite knowing their situation, but we don't know why she made that choice. It could've been malice, emberassment, indifference, spite, or even shame. We don't know how the loops changed her, or even if they did.

It really makes the plot twist stick in my head. Was her happily playing with Remnan an attempt to regain control over her pet? Was her rushing up to Gina and hugging her an expression of genuine affection? Was her friendship with Otome merely a convenience? Kukrushka being Manan reframes so much, but it's difficult to say what exactly it changes. What does it mean that Kukrushka is also Manan, who committed a number of atrocities and who abused Remnan for years? Does it mean everything she did was either evil or an act? Does it mean looping changed Manan and made her a better person?

setsu is a person whose life was only saved because of the silver key. their loops are an extension of their life. looping forces setsu to confront parts of themself, and to be a more proactive person. to address how emotionally disconnected they are, to grapple with making hard decisions, and to bend the rules when needed. they care deeply about protecting others, and the loops challenge that.

whereas yuri's loops mostly teach them to understand others, setsu's teach them to understand themselves. both of them come to care for the rest of the crew and for each other, to the point of making great sacrifices, even if done recklessly.

kukrushka is a contradictory existence, a confusing, inconsistent person who acts on her whims and does not try to understand them. she doesn't always care about consequences; her concern for them is unpredictable. she is a person half numb, ignorant to the well-being of others, someone who simply follows the tide of her loops. she does not try to escape them or to fill her key, she just rides, forever and ever, surrendering herself to time.