His twin sister, Hokuto, is a loud voiced, happy-to-be-alive teenage girl...Subaru's exact opposite. She expresses herself by wearing the most outrageous outfits she can find, ranging for cat suits to a Queen of Hearts costume. Ironically, she also dresses Subaru, but lucky for him, she tones it down a bit to match her brother's personality. While she does know some onmyouji as a member of the Sumeragi clan, she is not as experiences as Subaru.

One day, when he failed to catch a crow he was chasing (he tripped and fell), Subaru met Seishirou, a gentle veterinarian. Hokuto constantly teases Subaru about the couple getting married, and to Subaru's dismay, Seishirou usually joins in the fun. Seishirou serves as a confidant and support to Subaru in many occations (not to mention saving his life a few times).

Unfortunately, this series hasn't ended yet. Yes, Tokyo Babylon has finished, but Sumeragi Subaru's story continues into X/1999, another great work by Clamp. In this next series, Subaru meets a twin soul, another person who had to learn that living is so much more painful than death, and yet he must live for his "wish". I highly suggest that if you are reading X/1999, read Tokyo Babylon as well. It sets the background for Subaru and Seishirou making X/1999 even more worthwhile to read.