Miboujin Nikki: Akogare no Ano Hito to Hitotsu Yane no Shita

Both anime are about a lonely widow after her husband's death 

When one's husband passed away, there will be a sense of loneliness and the thirst for adventure arise. Any man who is in a position to comfort and claim the heart of that person would be foolish not to seize that opportunity.  

Both are about Young MCs falling in love with milfs.The difference is that while in Miboujin Nikki the Milf is a widow , in Hitozuma kasumi the milf s husband is still alive (BTW that husband is a piece of shit cheater who doesnt appreciatte how lucky he is to have a busty beautiful and delicious extra-fertile milf wife and cheats on her) 

+ Housewife having sex with her family members (Stepson in Enbo, Cousin in Miboujin) + Female MC (Misako Amamiya & Sonomura Ayako) can't express her love to Male MC (Ak-kun & Amamiya Kazuhiko) because they still love her husband + MC get seduced by another character (Yumika & Amamiya Emiko) but his love only for Female MC 

Similarity : MC is teacher who is in a relationship with her student (ex-student in Miboujin Nikki)