I get why it feels weird at first, but I see it more as the author showing that you cannot really control who you develop feelings for, only what you choose to do with those feelings. Kana knew she did not have a chance, and iirc she never confessed to Bota’s father or acted on it in any way. Instead, she respected the situation and continued to support them.
As for Bota developing feelings for Kana, from his perspective it feels understandable. Kana practically raised him after his father died when no one else was there.
She raised him, protected him, and trained him to survive. When two people spend years together in constant danger, relying on each other in life-and-death situations, emotional attachment is almost inevitable? I know that kind of bond does not sometimes automatically become romantic, but it is understandable that it could grow into romantic feelings over time (⌒▽⌒).

The story is really good but the romantic relationship between bota and kana is really weird She practically raised him lol, I pictured her as his old sister! It’s already weird as it is but kana actually loved his father? hell nah and the author gives us kiss scene between kana and the father really pissed me off. Even though it’s just her dream but still it feels like disrespect towards bota’s parents