Chapter 20

Sakamoto declares he has come to defend his employee. Studying a childhood photo, Tanaka recognizes the grown Shin seated behind Sakamoto and tells his driver, Seba, that he means to seize Shin before the lab kills him. Shin's telepathy confirms the group belongs to the Okutabi Lab. Tanaka releases three riders on separate motorcycles, each carrying an electric baton. Sakamoto shoves the first bike into a wall with his foot and pins its rider until he crashes, Shin borrows a plank from a passing lumber truck and jams the second machine's spokes, and Sakamoto flings himself and his own bike into the last pursuer's head.

With his squad wiped out, Tanaka ignores Lu's advice to apologize and instead grips her by the throat, insisting the lab's people are far more frightening. Shin scrambles onto the van roof to check on her, prompting Tanaka to summon Seba upward. Seba peels off his lab suit, activates an invisibility device, and vanishes, then knocks Shin off the vehicle and leaps onto Sakamoto's motorcycle. Sakamoto blocks the grab and clamps a hand around Seba's neck; Seba punctures the fuel tank and jumps back to the van just before the bike detonates. Learning that Seba never actually grabbed Shin, Tanaka decides to hand over Lu instead and races toward the lab.

Regrouping, Shin curses the loss of their ride while Sakamoto's tracker shows the van halting at the Okutabi Lab. Shin explains its role as a hidden underground research site and the place where he was raised, noting the workers' violence and gear were unfamiliar to him. The two set out to free Lu. Back at the store, Heisuke arrives with a coin he found and meets a tearful Hana, who missed her chance to mention Parents' Day; Piisuke suggests using its aerial search to locate the missing three, and Hana brightens as they send the bird aloft. Sakamoto and Shin finally reach the Okutabi Science Museum, the public face of the concealed lab and a spot Sakamoto had once brought Hana.

Tanaka's motorcycle team is defeated during the chase, and Seba debuts his invisibility suit before destroying Sakamoto's bike. Unable to capture Shin, Tanaka abducts Lu and drives her back to the Okutabi Lab. Shin reveals the lab as the underground facility where he grew up. At the store, Piisuke is dispatched from the sky to track down the missing trio, and Sakamoto and Shin arrive at the museum that fronts the hidden lab.

Titled Invisible Highway, this is the twentieth chapter of the series and belongs to the Lab Arc. It spans nineteen pages and was collected in Volume 3. Publication came on April 19, 2021, in the twentieth issue of that year. The cover shows Sakamoto, Shin, Lu Shaotang, Seba, and Tanaka.