7x7 - Dragon Ball Z: Dragon Box

After somehow managing to get Boo to promise to wait for one hour, Piccolo has Trunks and Goten go into the Room of Spirit and Time to train. The training is more or less successful, and when Boo cannot wait any longer, he is led into the Room of Spirit and Time. Inside, there is nothing of any great value that can be destoyed. At last, the all-out battle between Boo and Gotenks, with the future of the universe at stake, gets underway!