Mutations? I Have an Invisible Tentacle

Ten years ago, in a bizarre accident, Li Chen traveled to this world and passed by the Li Chen of this world. When Li Chen woke up again, he had returned to his appearance when he was 7 years old, just like Li Chen in this world. In this bizarre accident, Li Chen's family in this world was razed to the ground. His parents and toddler sister were also missing in the accident. In fact, it also includes Li Chen himself, because the Li Chen now is no longer the Li Chen of this world. The only 'survivor', Li Chen, who was only seven years old, also inexplicably received a tentacle that others could not see. The magical tentacles can be big or small, long or short. Can extend from any part of the body. The flexibility exceeds that of my own fingers. Moreover, this tentacle is still growing slowly. Ten years ago, strange 'black holes' began to appear in uninhabited areas around the world. Later, these 'black holes' were named 'secret realms'. This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.