I truly do not care whether it's a happy or sad ending, the only thing I want from this anime is for it to be canon. I'm hopeful since there's already a yaoi relationship but if it ends up being yuri bait trash I'm going to be so upset
I bet if Chisato lives, they'll just end it on a scene where they're holding hands.
HOWEVER, considering the final fight takes place in Episode 12, unless they somehow extend it to the final episode, I'd be willing to place some hopes that they're gonna develop their relationship a bit more before the end.
I know, inhaling too much hopium, blame that on the anime for dropping a sliver of hope in the form of extra heart, and super gay Takina in the spinoff light novel on like one week alone.