Complex sentence: Until March 31,2005, the district had only the town Kisogawa but on April 1,2005, the town of Kisogawa along with the city of Bisai merged into the city of Ichinomiya to become the new city of Ichinomiya.
Split into simpler sentences: Until March 31,2005, the district had only the town Kisogawa. But on April 1,2005, the town of Kisogawa, along with the city of Bisai, was merged into the expanded city of Ichinomiya.