Kanojo wa Ningu Musume!

Haruhito Kasuke was ordered by his mum to find an item in the storage house. Being a shopping-holic, Kasuke's mum had caused the storage house to become a dumping ground of unknown goods. Kasuke accidentally found an old ninja katana in the storage house, and the katana suddenly changes into the form of a kunoichi (female ninja). "I had waited a long time and I finally get to see you again.."