Miwa wants to get romantically involved with him, but cannot. Soon she finds herself attracted to his father. A dangerous triangular love affair goes on.

From TCMANGA:
Emily, a 23 year old woman, is a teacher at the local high school. She's smart, attractive and put together--well it would appear that way. What has been kept a secret however from everyone else is that she is actually married to Shishio--an 18 year old student in her class. Lots of hilarious circumstances ensue along with some romance and some real life issues between the couple.

The prequel book Atashi no Lion starts the series, and then it becomes My Darling Lion and continues on for 10 volumes.

From Nekohana:
Rich young Master comes across a girl alone and abandoned during Christmas. He decides to take her in and name her "Mike". Now he's in high school and she's his personal maid. Did I mention she now loves him and he's rather sadistic with a terrible panty fetish?

Emiri, a 23-year-old high school teacher, makes love once with 18-year-old Shishioh (meaning Lion King) and they decide to get married. Shishioh transfers to the school where Emiri teaches.

The summer vacation...with a teacher in a vacant classroom. It is a sweet painful love affair that a girl often (o rly?) experiences. This is the sixth issue of the best-selling Cheese selection. Nine other stories are included besides the title story written by Sugi Emiko.