Based on the erotic game by Blue Gale.

The feisty Natsume, motherly Akira, soft-spoken Fuyu, and innocent Haruka make up the Makino sisters. One week after losing his wife in an accident, the father of the household, Kenichi, starts to view his four daughters in a way that goes beyond a regular parent-child relationship. He soon becomes unable to resist their beautiful figures, and giving in to his carnal incestuous desires, he starts to have his way with them one by one.

(Source: MAL Rewrite)