Shinobu then brought Misora along when he went to confront his son, Sento Kiryu. Sento found Misora in an abandoned warehouse, walking towards him. Vernage then surfaces and maddeningly demands to have her planet back before transforming into the CD Lost Smash and attacking Sento. Sento initially fights the CD Lost Smash in his Build TankTank form, but later switches to his Genius Form after TankTank proves ineffective. Shinobu soon shows up and transforms into Kamen Rider Build with his own Build Driver and faces off against Sento as well.
During the fight, Shinobu reveals that because of the high level of Nebula Gas Misora was exposed to, she is unable to be purified. The two then beat Sento down and cancel his transformation, leaving him lying hopeless on the ground. However, Ryuga Banjou then arrives to offer assistance and encouragement to Sento to continue fighting on.
The two heroic Riders then take on Shinobu and CD Lost Smash again, and Sento manages to save Misora by transferring Vernage's essence from her to Ryuga, reverting her back to her human form and creating the CD Lost Bottle. Shinobu attempts to seize the Lost Bottle, but is knocked out of his transformation by Sento and Ryuga, prompting him to retreat.