Pretty Guardian Sailor Moon S01 E07 Someone Saw Me Transform!

Usagi suspects that a Karaoke Crown attendant named Motoki Furuhata is Tuxedo Mask when she discovers a tuxedo jacket with a hole in it like from the battle the night before, and impulsively brings him a gift. Makoto and Rei are invited along with them to an amusement park where they meet two of Motoki's friends - one of which is Mamoru Chiba. Things go well until a Youma attacks Rei, and Usagi unknowingly reveals to Mamoru that she is Sailor Moon.