1x43 - Pretty Guardian Sailor Moon

A life-taking stone has been implanted into Mamoru's body by virtue of Queen Beryl's trap. The more he loves Usagi, the closer he creeps to death. Knowing this, Usagi's anger rises. And with that Usagi changes... Having realized this change, Mamoru is determined to meet Usagi, regardless of the stone's existence within himself. His grace period is until sunset, and if he doesn't return Queen Beryl will take his life.