Subaru is the third heroine in the Eroge game Beat Blades Haruka, produced by Alice Soft in 2008. She is also one of the main character in the Hentai three episodes series Beat Blades Haruka, produced by Milky, in 2009 and aired from Aug 25, 2009 to Sep 17, 2010. What is more curious about this character is her/his gender. Subaru seems to be hermaphrodite (or how is called in Japan, a futanari).
In the plot, Takamaru is a student at the Ten Treasure Academy, living an ordinary school life, seeking romances which are constantly interfered by Shihoudou Narika (the daughter of his apartment manager). One day, he fell in love at first sight with a transfer student named Takamori Haruka. On that very night, Takamaru and Narika became pursued by a group of mysterious ninja. Just when they thought all hope is lost, Haruka appeared in kunoichi attire. Haruka referred to Takamaru as “young boss”, and asked him to do “H” stuff towards her. This gave her superhuman power that enabled her to defeat the mysterious ninjas.
If you just like me, you don’t know much about the Hentai universe, Beat Blades Haruka (also known as Choukou Sennin Haruka) is a Eroge game (or H-Games, a kind of video game that has sexual content, that are very popular in Japan), and in almost all Hentai stories the heroes and heroines usually get their superpower after some sexual stimulation. Sources: All The Tropes, My Anime List, Tenka Seiha.