Koyomi... My Issues with the character.

All I can say is that Koyomi is one character in the original manga that I do not like, at least in her manga incarnation.  Basically, Koyomi makes a quick turn to joining Den and the Barjack rebels along with cheering on Den killing people by the hordes, as he carries her along.  The part that hurts more is the fact that Alita, and also Kaos, has just acted to save Koyomi and help her a bit before she decided to join Den, not to mention she said just wanted to go help Alita.  Either way, the original character comes off as pretty unlikeable, and raises a lot of questions as to what is going on regarding her motivations.

 

    In the film version, she already starts off as a teenager working with Hugo's gang, including taking part in the crippling and dismantling of Kinuba in the streets.  Her adoptive father Walsh is also shown, and the bar got trashed by a brawl that Alita started with Zapan that got the various Hunter Warriors involved.  That fight also made Hugo into Zapan's target, as retaliation for the humiliation in the bar.  All in all, with the near death of her father and Hugo's death, along with her boyfriend, Tanji, caused by Alita's actions in the film, Koyomi from the film has a more apparent motivation to be upset and hostile to Alita early on given what happened, along with her possibly assisting Nova and/or Den with that motivation.