Throughout August Serial⇔NUMBER performed all over the country again, this time as part of SPEED DISK PRESENTS Shinrabanshou TOUR'06#2, and on the 20th their current bassist Hibiki joined. Their spring tour ended in early June and the next month saw the release of their second maxi single, Orion to hanabi to tabidatsu doushiguwaa tachi e. On May 10 the band's first maxi single, Hibiscus mile home, went on sale. Bassist Tama left shortly after, and Serial⇔NUMBER then embarked on their spring countrywide tour, Road to Shiisaa. Their live activities continued during 2006 at a variety of venues, and their drummer Kai joined the band in March.
After their first live in July at Takadanobaba AREA, they continued to perform there and at Shinjuku club HOLIDAY regularly for the rest of year. The band formed in April 2005 with vocalist Sasaki Jin, Kazune and Shiyuu on guitars, and Tama on bass.