D.N.Angel

D.N.Angel is a manga series that received an anime adaptation which aired in 2003.

The story follows Daisuke Niwa, an average middle school student who gets rejected by his crush on his fourteenth birthday. After then undergoing a sudden and strange mutation, he is informed by his mother that the phenomenon is the result of a genetic condition running in Daisuke's family that causes males to transform into the legendary phantom thief known as Dark Mousy whenever they think about their unrequited love. Daisuke is made to keep this revelation a secret, and is tasked by his mother to control Dark and steal valuable works of art for an unknown purpose, while learning that having his love returned is the only way to turn back to normal.

Episode 1
Daisuke transforms into Dark Mousy for the first time.

Episode 4
Satoshi is sitting on his bed when he gets a call from his father.

Episode 8
Daisuke looks at Dark in the mirror's reflection.