I just heard this one on today's episode of NHK's "Nodo Jiman" performed by a couple of ladies from Chiba Prefecture which jogged my memory of Mayo Okamoto（岡本真夜）. She certainly became an overnight sensation with her debut song of "TOMORROW" which was released back in May 1995. It just seemed like every time I turned the TV on back then, there was that cheerful song once again.
"TOMORROW" was written by Okamoto with Anju Mana（真名杏樹）providing the music. Initially, it was known as the theme song for a TBS drama, "Second Chance" starring Misako Tanaka and burly Hidekazu Akai as single parents who decide to hook up against outside objections. According to J-Wiki, the song had originally been written as a ballad to cheer up a close friend but during the creation of the drama itself, the producer requested that it be made into a much more uptempo tune. Apparently it was a wise move since the song would hit No. 1 on Oricon and become the 8th-ranked song of the year. Okamoto herself made her television debut on the Kohaku Utagassen on New Year's Eve to perform it. It eventually sold over 2 million copies.
I recollect "TOMORROW" being sung a ton of times at karaoke and I wouldn't be surprised if it has been sung at various celebratory events such as graduations and weddings. It was used as the entrance song for the 68th High School Baseball Championships at Koshien Stadium in March 1996. In terms of the encouragement level, I think it rates up there with another song with the same title sung by a certain curly red-haired girl.