Magical Girl Lyrical Nanoha (spinoff) Triangle Heart (とらいあんぐるハート, Toraianguru Hāto), abbreviated as Toraha, is a series of eroge by Janis and OVAs by Mook and Seven Arcs that is best known for its spin-off series, Magical Girl Lyrical Nanoha.
The 2003 Triangle Heart: Sweet Songs Forever (とらいあんぐるハート～Sweet Songs Forever～) OVA, based on the game Triangle Heart 3, focuses on a boy named Kyōya Takamachi who, with his cousin-turned-sister, vows to protect a childhood friend from a mysterious terrorist organization.
Triangle Heart: Years ago, professional bodyguard Shirō Fuwa and his client Albert Crystela were killed by a terrorist organization that is known by the symbol of a clover leaf.
Albert's daughter Fiasse blamed herself, but then grew closer to the Fuwa (now Takamachi) children, Kyōya and Miyuki, and decided to use her gift of singing to help the world.
Kyōya and Miyuki, swearing to protect Fiasse, become professional bodyguards like their fathers.
Triangle Heart 2: Sazanami Joshiryō: Kosuke Makihara works as a substitute janitor of a huge boarding house called Sazanami Dormitory mostly consisting of young girls from grades of elementary school through high school, while the regular janitor and the dorms owner, who is his brother in law Keigo and his aunt Kana respectively, are traveling abroad in Hong Kong, China.
He is Shinichirō's classmate, and the only other male character, filling a role much like Jun Kitagawa of Kanon.
Miyuki does not really feel any passion for sword fighting, but does it because she wants to honour Shirō and protect Fiasse.
Her father and extended family were killed by the clover-leaf terrorist organization, so she was adopted by Shirō while her biological mother sought revenge.
Fiasse is a world-renowned singer and heiress, and the childhood friend of Kyōya and Miyuki to whom she is an older sister figure.
She comes from England, but lives in Uminari City during the game and returns to Crystela Song School in the OVAs.
A character from the OVAs, Ellis is Fiasse's real (read: paid) bodyguard, and jealous of Kyōya and Miyuki.
Akira is a friend of the Takamachi family, who got a scholarship in Uminari City and so moved into the Midori-ya.
She was cursed to live forever, but was sealed into the form of a helpless young fox until the Kanzaki family could become powerful enough to either save or destroy her.
Noel is Shinobu's robotic maid, built by her aunt Sakura to be her constant companion.
She now owns the Midori-ya (翠屋, Midori ya) cafe, after retiring from her job as a top chef.
Nanoha is the youngest Takamachi, and has no need for swords, as she, around twelve years old, is almost completely removed from the conflict.
In the Lyrical Toy Box game, even though she has passed to the spirit realm, her influence is felt everywhere.
Fiasse's mother, Tiore, is the aging wheelchair-bound director of the famed Crystela Song School.
In the OVAs, she has died and left Fiasse with an inheritance that she can claim once she reaches a certain age or marries.
Misato is actually Miyuki's biological mother, who infiltrated the organization and worked her way up to learn the leader's name.
In the OVA, Misato is the commanding officer of the Hong Kong Intelligence Defence Squad's 4th Division, and plans to recruit Kyōya and Miyuki into her team.