The blond died during the black hair guy's birthday. A year after, the black hair took a trip with the blond guy's soul or if the black hair guy imagined him to be alive then (that's why he is getting looks from people around him when he talks or laughs because he is alone). At the last stop, he confessed how difficult it is to leave while the blond guy's soul tries to stop him. In the end, it was implied that the black hair guy jumped and died.
omg now im twice heartbroken thank you for the explaination
I thought it was a flashback this is making me cry even more now whatttt
who died actually? the blond or the black hair guy called seiji?