Based on the CG collection by Yakisaba Teishoku (焼鯖定食).

Rinka, who was bored by her father for being tired of her being home late, planned to stay at her uncle's house. Her uncle was annoyed by Rinka's arbitrary attitude at home, in connection with a past that had once liked Rinka's mother named Haruka before marrying her father. Therefore, Rinka's uncle was planning evil to vent his passionate desires to her who resembled Haruka with a stimulant drug that he got working outside the city.

Note: This uncle is not a fat and ugly character in general, but a young person.

(Source: Translated and Edited from Nekopoi)