Complex sentence: Meanwhile, Kondō Isami, leader of the "Shinsengumi", after having withdrawn his remaining forces after the Battle of Toba-Fushimi back to Edo, met with Shogunal military commander Katsu Kaishū.
Split into simpler sentences: Meanwhile, Kondō Isami, leader of the "Shinsengumi", withdrew to Edo after the Battle of Toba-Fushimi. Once back in Edo, he met with Shogunal military commander Katsu Kaishū.