I'm degen enough to not mind the incest, even dig it most of the time, but I also vouch for non-incest for this one. By the setting of this story, it'll be much more whole some and satisfying if no romantic feeling is involve in his quest to help her.
It isn't literal incest anyway. In Japan cousins can marry and she his the mother's sister's child and (with the last name different) she was only taken in and not adopted.
I'm not sure of the chapter that was revealed in but I have it in my notes:
Konno, Komaru (F)
o) FL
o) Age: 21
o) Blonde with black roots
o) Multiple ear piercings
o) Attends Hishou Public HS in Hiroshima, a correspondence school for anyone over 15 that has 3-6 in-class days per month
o) Shinji's "stepsister" (actually first cousin being raised by relatives after being "thrown away" by her birth mother, Shinji's mother's sister)
o) "Cheeky (Dirty Slut) Gyaru"
o) Very abrasive towards Shinji but at one time was very close
o) Easily manipulated by pressure that she'd be alone
o) Read phonetically her whole name means "this troubled (girl)"
o) Tricked into going to a drinking party by a "friend" who promised it would just be the two of them and forced into guzzling booze (which she is weak to)
o) Stood up to Youhei when she went to get her purse left at the attempted rape party and he tried to intimidate her into staying
o) Bothered that Shinji was confessed to (that's how he's spinning it)
o) The Shinji in her heart is a 5th grader covered in mud
o) Abused by both biological parents
o) Diagnosed with depression and PTSD