Kouta Sasaki (佐々木 弘太, Sasaki Kōta) is one of Tobio's friends who went missing in the Luxury Liner Incident.
Months after his disappearance, Tobio accidentally came across Sasaki along with Sae, chasing after Sasaki. Upon reaching Sasaki, Tobio is shocked to see a lizard like monster attached to Sasaki and his devoid of emotion look. The Lizard Monster then attack Tobio but was defeated by the timely rescue of Natsume Minagawa, who defeats the Lizard Monster. Defeated, Sasaki faints and is teleported by a magic circle.
Later, Tobio encounter his friend again, this time however, Sasaki and the other students were under the leadership of Kazuhisa Doumon who ordered Sasaki to kill himself with Tobio's Sacred Gear, an act that angered Tobio.
Lizard Utsusemi: Sasaki's unnamed Utsusemi, it takes a form of a giant lizard with a tentacle like tongue that can be used to attack.