Season 0 of 스트린젠도～천사들의 개인레슨～ premiered on May 25, 2012.

Season 1 of 스트린젠도～천사들의 개인레슨～ premiered on January 27, 2006.

Tomohisa and Endou aren't either so handsome or ugly; they are just normal boy students. They're looking at Mizuho, the senior student, and Mikura, their classmate. Mizuho is a returnee student, and she attracts all the students by her beauty. Mizuho notices their eyes, and she gives Tomohisa a suggestive look.

One day, Tomohisa finds a note in his desk. It says, "I'm waiting in the ladies' room on the third floor". He goes there and finds Mizuho is waiting for him...

The next day, Tomohisa can't help recalling the event the day before. He happens to find that Endou is gone, and also Mikura, whom he loves secretly, is missing, too. He's afraid that they're doing things. However, exactly, they're doing things on the fire escape.

Season 2 of 스트린젠도～천사들의 개인레슨～ premiered on January 26, 2007.

Waitress Tamaki has sex with her playmate Kurono at the café she works for. Ignorant of their relationship, their common friend, Ohashi, visits the café as usual to see Tamaki whom he secretly loves. However, Kurono notices Ohashi’s feelings. In order to incite him into confessing his feelings to her, Kurono molests Tamaki and makes her wait on him as she is. As she was sexually excited, she gives off a female's scent, which, in turn, excites Ohashi.

Season 3 of 스트린젠도～천사들의 개인레슨～ premiered on May 23, 2008.

Mizuho stays after school to teach some students some equations, but that is not all there is to it. She also invites her boyfriend, Tomohisa, for some excitement. While giving those students the lesson, she is also giving Tomohisa a handjob; she even goes as far as to giving him a blowjob right then and there.

After all that hot action going on, Mizuho invites Tomohisa to her house to continue their good time together...

Season 4 of 스트린젠도～천사들의 개인레슨～ premiered on May 29, 2009.

Ruma is the most beautiful and popular girl on school, she acts nice and polite with her classmates and friends, but she has a side that almost every male student knows and that is that she has the perfect sex body and she likes to have sex with any student she wants, where she wants and when she wants. Actually she only feeds with the sperm of her sexual encounters. The couples from Stringendo & Accelerando also appear in this OVAs and are Stretta's photo-targets so she can masturbate later with their sexual encounters. (Source: ANN)