Satoshi Osugi is a member of the Eden of the East friend group and business team who harbors unrequited romantic feelings for Saki Morimi. These feelings significantly influence his interactions, fueling persistent jealousy towards Akira Takizawa. Osugi repeatedly attempts to discredit Takizawa, especially as Saki grows closer to him, including actively blaming Takizawa for the Careless Monday missile attacks and the kidnapping of 20,000 NEETs.

Saki later disproves these accusations by demonstrating Takizawa's efforts to protect the victims. Osugi experiences frequent social mishaps within the group, often being disregarded by others and facing drunken incidents. One such incident, involving misplaced belongings, leads to a case of mistaken identity where he is confused for a serial rapist. Physically, he possesses light brown hair and matching eyes.

During the events of Paradise Lost, Osugi assists Saki in locating Takizawa's mother, Aya. This search is part of their attempt to uncover Takizawa's family background and potential connection to the deceased Prime Minister, Iinuma. Their pursuit leads them to Aya's bar, though she avoids confirming Takizawa's paternity and flees upon the arrival of police.