I need a bl w this scenario

It has to be bl bc like listen, two dudes, best friends, never acknowledges their feelings for each other, one dude has a sister, total thirdwhee, but brother has to go somewhere idk military or something but he has to go somewhere so like he tells his best friend to take care of his sister, and dude takes care of herz protects her fr, but they fall in love with each other so um this actually isn't bl injust need it to be tragic as FUCK