I gotta say that the official video for this song is probably one of the brightest I've ever come across, at least when it comes to the singer's close-ups. And it looks like Noriyuki Makihara （槇原敬之）and the director really had a great time filming it.
Makihara can make some of the most heartbreaking ballads and some of the most uptempo feel-good songs in J-Pop, and "No. 1" is definitely one of the latter variety (as any song with that title would have to be). Released in September 1993 as his 8th single, along with the happy-go-lucky music, his lyrics make for a fellow's plans on how to create one splendid wonderland for his beloved. He's the No. 1 guy after all. And he knows that she knows he's No. 1.
Not surprisingly, "No. 1" did indeed hit No. 1 on the charts. However, it didn't fare as high on the 1993 yearly charts, peaking at No. 41. Still, I have no doubt that the song is one of the regular entries on any of his BEST compilations. The song was also a track on his 4th album, "Self-Portrait" which came out on Halloween in the same year. It also hit No. 1 and despite its late release in the year, quickly became Album No. 12 on the 1993 annual charts, breaking the million barrier.