lovvlai's manga / #Sibilings(1)

it was interesting... -on an arranged marriage meeting, natsumi and her sister haru is set up with rich guy tougi?? haru and the guy starts dating, become fiancee..but she has cancer and died at the age of 19. now natsumi goes out with her sister's boyfriend to the places that they date before in order to remember her. but they both end up falling and date each other in the end. --they carry guilty feelings about the sister, they both kind of want to die... --natsumi actually had romantic feelings for her sister?