This tag is to be used if the appearance of the protagonist ONLY is different from their actual age. This tag can be used to describe the protagonist of a cultivation novel who doesn't age despite being very old, though it is not recommended as it can become a very generic tag. Best to use this tag only if the fact that the appearance is different from actual age is actually used in the story.

Please note that the age mentioned is physical age, and NOT mental age. That might come under the Mature Protagonist tag.
This is the story of a young slave gladiator in an underground arena. He doesn’t know about his past or how he got to where he is, only that his name is Aegir, and that he is strong. One day he kills the boss and escapes the arena, joining a band of mercenaries as a new recruit. During one mission, they encounter the vampire, Lucy, who slaughters the band with her inhuman strength. After learning that Aegir only knows how to kill, Lucy lets him stay at her house, educating and taking care of him. Two years pass, and on the day of Aegir’s departure, they both exchange a promise that if Aegir becomes a king and owns the land of Erg forest, he can come and take her as his woman. Making this his life goal, Aegir set out on a journey to become a hero, a king, and found his own kingdom.
When I cleared the final chapter of a game that was a national failure, I became an unnamed side character in it. A non-standard, unmeasurable, EX rank supporting character.