Itsuwari no Daishou

Part of a collection of oneshots called ‘Mijuku na Kareshi’.
When teenager Mahito sees his father and his father’s secretary Kazaoka having sex, Kazaoka is sure that Mahito hates him. But then Mahito’s father dies and he takes over the company and Kazaoka!
According to MyAnimeList, this is part of a collection of one shots. The order goes like this:
1) Aimai na Kankei
2) Yasashiku Toraete; sequel to (1)
3) Itsuwari no Daishou (False Compensation)
4) Man On!
5) Kodomo Ijou Otona Miman
6) Sweet Restraint; (Amai Kousoku)
7) Miracles Don’t Happen (Kiseki wa Okorenai)
8) Mijuku na Kareshi; extra to (7); (Childish Feelings; Immature Feelings)