The island of the summons

The Summoning Island.

The Summoning Island (口寄せの島, Kuchiyose no Shima) is an island located somewhere east of the Land of Fire and south of the Land of Lightning where research of summoning animals and development of them were done. The Ultimate Summoning Beast was also created there. The lab was located in the mouth of a volcano and on one fateful day, Honoka, a kunoichi that the researchers had recruited, was unable to restrain the beast after it had gone berserk killing all of them. Honoka's spirit remained on the island, unable to move on until the delegation from Konohagakure came and helped her defeat the beast completely.