Nikkan Tachibana

From MangaHelpers:
It's been 10 years since the mother of the Tachibana family passed away. Now, for the first time in 10 years, Shigeru (18) will be introduced to his new mom: Kaoru. Kaoru is a 20-year-old virgin and still only a student. Shigeru can not hide his sexual frustrations while living with his new, sexy mother. His sister finds Shigeru to be immature and almost comical, while his father seems to be oblivious of any tension created by the introduction of the new family member. Shigeru will have to use all of his willpower to withstand the seductive situations Kaoru puts him through.