The monster, Cosmo Liquid, attacks a construction site by a river in the outskirts of Tokyo. Investigating the case, Kotaro finds the monster and shoots it, but it mysteriously disappears. The monster has transformed itself into liquid and moved to central Tokyo along the flowing river. Kotaro transforms into Ultraman Taro and defeats Cosmo Liquid, which is swallowed into a mysterious pit that is rumored to devour anything. The next day, Kotaro himself accidentally gets swallowed by the pit. Hope is not lost, however, as Mother of Ultra is heading to Earth...
多摩川の工事現場に怪獣コスモリキッドが現れた。怪獣は体を液体化させ姿を消すがＺＡＴの放電作戦で姿を現し、ウルトラマンタロウに倒された。翌朝、ランニング中の光太郎は、謎の穴の中に落ちてしまう。行き着いたのは、怪獣ライブキングのお腹の中だった！
