Sega is the name of more than one artist.
1) Sega is a hop-hop artist.
2) a variation on Richard Sega
3) referring to DJ SEGA
But most likely it appears here due to incorrectly tagged video game soundtracks. If this non-artist appears in your charts, do last.fm and yourself a favour. Fix your tags by putting the actual artist name in the artist field. The easiest is to use something like Picard.