Pirachu is a strange mouse villain who first appears in Hyperdimension Neptunia Mk-2. He sometimes appears alongside Linda, who happens to dress in similar themed clothing resembling Pirachu. He believes himself to be the official Mascot in his world/land/town, filled with other Mouse like himself.
After being injured, then healed by Compa, Pirachu develops a crush on her.
Pirachu has a lot of confidence and is loyal to Arfoire, but is quick to retreat should he lose a battle. As explained above, he has a crush on Compa, believing her to be an angel after she offered to heal his wounds. He holds Compa in high esteem, even when she views him as an enemy.
During battle he frequently talks about Compa, who has no idea he likes her so much or holds any affection towards her. He often calls her "Compa-chan" or "my sweet Compa".
Pirachu is a small gray mouse with two white whiskers on each cheek and big red eyes, appearing almost lifeless. While he has black coloring on his arms, legs, and inside of his ears. He possesses two small red-purple demon wings and a rat-like tail with a big black heart on the end and a zig-zag split in the center and resembling a fork tail.
On his chest is a red and yellow broken heart marking and he wears red boots.
- In the Japanese version, he is voiced by Neeko. Ironically, Neeko is close to neko, Japanese for "cat".
- The "chu" in Pirachu comes from "Chu", a noise a mouse makes in Japanese sounds.
- The manga hints that Pirachu is not an original being, but that several others of his species exist.
- Pirachu has come in 20th place in a recent popularity poll.
- Pirachu's name is a reference to Pikachu. But the "Pira" may come from "Pirate", which is an illegal copy of a game someone has made or sells.
- Pirachu's Japanese name "Warechu" may come from "Software".
- Pirachu is one of the few characters lacking a physical change between games.
- Pirachu states that he is one of the three most popular rodent mascots in the world. This may be a reference to Pikachu from Pokemon and Mickey Mouse of Disney fame.