Shounen no Natsu

Overview

The story is set at a beach, where a young boy walks in the sand before sitting down. Crowds come in to enjoy playing in the ocean, and then leave, with trash scattered all across the sand behind them. Suddenly the scene jumps to a hospital office where an old man with a cigar is telling a younger, thinner guy something about cancer, the amount of money involved, the idea that the money might stay in the family, etc. Then the scene shifts back with the boy standing up, brushing the sand off his seat and walking back home.

Source: AniList