The Soul Diver (ソウルダイバー Sourudaibā) was one of Kururu's inventions.
The Soul Diver was a machine designed to enter and alter one's memories at will.
What the Soul Diver does is it putting Keroro, Giroro and Tamama in the ball Dororo was in that will make them go in Dororo's head that will go to his memories.
The Soul Diver makes an appearance again in the 158th episode of the anime, where the Keroro Platoon and Pururu enters inside Giroro's memories. However, it seems Kururu is enjoying himself tweaking and manipulating Giroro's memories such as changing love of Natsumi into love of Kururu or changing Natsumi's face into Kururu's, which made Giroro frequently shrieking in panic as he goes out of control and destroyed the entire Soul Diver. After Giroro's release, he found out that Kururu was blushing at him for some reason, making Giroro feel a bittersweet feeling inside his heart. However, when he finds out that Kururu was actually loves him, the entire platoon (including Mois and Kururu) were concerned on whether Kururu was interested in Giroro or that he was just making fun of him. Giroro panics, as he constantly shakes Kururu telling him to change his memories back now. However, Kururu didn't listen, and Giroro screamed in agony at the end of the episode.