Me, the Cat and the 20-year-old You

Rintaro Waga is a lonely old writer. He has quit his job, and now his only reason of living is to take care of his cat. One rainy day, Rintaro wanders into a shrine led by his cat, gets trapped into a pond and start drowning. He prepares to die, but is saved by his only friend Shiyo, who died 40 years ago. (Source: Coamix, translated)