Director Nagashima initially appears as a high-ranking official with the canal project's construction company, held hostage aboard the luxury cruiser Double Sea during its terrorist sea-jacking. This status makes him a key rescue target for anti-terrorist unit Team Wild. However, his role reverses when he is exposed as the mastermind orchestrating the sea-jacking and hostage crisis. His core objective is sinking the Double Sea within the newly built Panama Canal's block 3 to permanently disable the canal.

Nagashima shares a past with Team Wild member Japo, having commanded him under the alias "Wolf" in a former mercenary unit. This history fuels their adversarial dynamic during the crisis. To achieve his goal, Nagashima employs ruthless tactics, detonating explosives aboard the ship to thwart hostage escapes and eliminate his own operatives. He demonstrates meticulous planning, concealing a critical bomb trigger within the hair accessory of Shino, an ex-member of the original Wild Seven unit.

He commands the Ancient People's Army, the ground troop supporting the sea-jackers, and controls collaborators like a ship doctor tasked with eliminating threats. Nagashima secures a significant portion (70%) of the ransom into a Swiss bank account before taking direct command of the Double Sea operation. The climax unfolds as the ship enters the critical canal section. Despite Team Wild locating the hidden trigger and facilitating hostage evacuation, Nagashima confronts Japo directly aboard the vessel. The Double Sea explodes during this final encounter.