Katekyou Hitman Reborn!

Synopsis

After they finished practicing on the airbikes, Reborn tells Tsuna and his friends they shall train tomorrow on opening their respective Vongola Boxes. Tsuna's box weapon shakes violently that evening and Tsuna opens it and releases his box weapon. Tsuna's box weapon attacks him and with the help of Yamamoto and Basil, they are able to seal the box weapon back to its box. Dino arrives and tells Tsuna his box weapon attacked him because he opened it incorrectly and comments that the Sky Box Weapons must be used delicately.

(Source: Wikipedia)