Jiburiru

A series of X-rated visual novels by Frontwing. As of August 2011, there are five games in the series, with OVAs of the first two games completed and one based on the third game in progress.

The first three games (Makai Tenshi Jiburiru (Devil Angel Jiburiru)(2004), Makai Tenshi Jiburiru Episode 2 (2005), and Makai Tenshi Jiburiru Episode 3 (2008)) center around Naoto (the player character) and his childhood friend Rika. When an apprentice angel named Lovriel comes to earth to counter the demon Asmodeus, she finds herself out of her element and must rely on Rika to transform into the legendary angel Jiburiru in order to fight the forces of Hell. (Un)fortunately for the young couple, the only way to charge Rika's new power and unlock stronger attacks is to subject her to various varieties of sexual stimulation. The fights against Asmodeus cover the first game, while Episode 2 introduces Naoto's little sister Hikari and a new antagonist, and Episode 3 introduces the artificial angel Nagi and another new antagonist.

The next two games (Makai Tenshi Jiburiru Episode 4 (2010) and Sengoku Tenshi Jiuriru (Warring States Angel Jiburiru) (2011)) feature a different cast of characters, but a similar premise: Loveriel comes to earth to thwart the minions of Hell and their plans, but isn't quite up to the task and is forced to rely on local manpower to complete her mission. This time, she recruits Momo, Aoi, and Yuzuha to fight demon twins Maimai and Meimei, with the help of their fellow student council member Kento. Sengoku introduces a time travel plot, and also includes Rika, Hikari, and Nagi from the first three games.

Jiburiru contains examples of

 * Brother Sister Incest: Between Naoto and Hikari in games 2 and 3.
 * Butt Monkey / Chew Toy: Meimi Otonashi/Misty May from the first three games just can't catch a break.
 * Casting Gag:
 * Izumi Maki plays antagonists in all five games: Meimi/Misty May in the first three, and Meimei in the next two.
 * In 2006, two years after the first game, Frontwing released Megachu!, which also had Yukari Aoyama and Nana Nogami's characters teaming up to fight Maki's character.
 * Combat Tentacles / Naughty Tentacles
 * Deus Sex Machina / Intimate Healing: Sex is required to recharge energy and learn new combat skills.
 * Love Makes You Evil: Meimi Otonashi from the first three games. This manifests in a Superpowered Evil Side named Misty May.
 * Magical Girl
 * Really 700 Years Old: Loveriel's age is officially listed as 10,009 as of the start of the first game.
 * Spell My Name with an S: As this page name implies, the official spelling "Djibril" isn't very popular among Western fans, who generally prefer "Jiburiru" or "Jibril". There's also Loveriel's name, officially spelled "Luvriel".
 * Retcon: The first game initially made it clear that Naoto was an only child. The second game introduces his little sister Hikari, back from a stint as a foreign exchange student in Italy.