Anime fans, I need help!!

Ok, there's this Anime TV mostra I watched a long time ago, and now I can't remember the name of it. For te Anime fans, can te help me find out what's it called?

1.it was about a guy who went into his room one giorno and found a kid-like person in there. There was also a book(I think it was red). When the guy read the first line of the book, lightning struck his house, and he found out he made the kid preform a spell

2. the kid is from another dimension-thing where every number of years, they have to go to earth, battle, and the last person standing becomes king. o something like that.

You'll get props of te can tell me what this is!!Please help me!!