Selkie/Synopsis

Vs. Hero Killer Arc
Selkie accepts Tsuyu Asui's request to do her Hero Agency Internships with him at the Oki Mariner. From the first day he put her to train with the rest of the crew or to maintain and clean the ship. One day, he finds Tsuyu and his sidekick Sirius sitting down and scolds them for slacking off. Sirius corrects him, stating they had already finished their tasks. Selkie apologizes for jumping to conclusions, using his cute persona, much to Sirius dismay, who reminds him that he cannot be adorable because he's too rugged for that, which puts Selkie off.

One of his crewmembers says they've received a mission from the guard coast. Selkie immediately gives his crew the order to set sail, and during the journey he explains they are requested to patrol a certain area in search of stowaways, as they have been on a trade ship called Nysan to which part of its cargo disappeared was missing. He asks Tsuyu about what she thinks about it. She replies that the stowaways were probably smuggling brokers who moved the cargo to another ship and fled before the arrival of the guard coast. Surprised, Selkie tells her that she is right.

Selkie takes to the water himself to search for the ship using his Spotted Seal Quirk capabilities while the rest of the crew search via radar. They search for hours and it gets dark, but they can't find anything. Then they are informed that a fishing boat thought to belong to the stowaways is in their area after escaping another pursuer. Selkie returns to the ship after confirming the location of the boat and they eventually happen upon it.

Selkie and a couple of his crewmates board the fishing boat. Tsuyu wants to participate but Selkie denies the request and orders her to stay on the ship, much to her dismay. Selkie and his men interrogate the alleged fishermen, but are fooled and locked in one of the ship's holds. The stowaways run away, but Selkie uses his echolocation ability to inform Selkie that this boat was a decoy and they must pursue the real stowaways.

As Sirius, Tsuyu, and Mick follow his orders, he manages to escape the fishing boat. He contacts Sirius's group without knowing that they are at the time facing the criminal ringleader Innsmouth, but Tsuyu relays an S.O.S across using Sirius's radio. Selkie swiftly swims to their aid, and along the way defeats the villain's lackeys. He finds Tsuyu and Sirius overpowered by Innsmouth himself. Innsmouth blinds Selkie using his ink, but he uses echolocation to find and defeat him. Afterward, the stolen goods are returned and Selkie claims that Tsuyu will make a great hero one day.

Shie Hassaikai Arc
When Class 1-A was told that only Hero Offices with good histories were allowed to accept interns, Tsuyu considered calling Selkie. Unfortunately, Selkie's agency did not meet the proper standards, and Tsuyu interned under Ryukyu instead.

Endeavor Agency Arc
After a ship suspected of smuggling Trigger got away using a massive smokescreen, Selkie teams up with Ryukyu and her students. He then tells the girls to relax on the beach to improve their morale, before heading out to find the ship at sunset. At sea, Selkie and Tsuyu head underwater to locate the ship before sneaking on top of it. Using his echolocation, Selkie locates and defeats two smugglers using Selkie Punch, but the drugs have already been transported onto a cargo ship, which began to take off.

Ochaco manages to take down the smuggler flying the plane, and Ryukyu safely lands the plane on the water. They find Trigger in the ship and are glad that they stopped the smugglers in time. Later, when the girls are relaxing once more, Selkie and Ryukyu discuss their findings, including that the smugglers were couriers for an anonymous employer and that the drugs were headed for Otheon in Europe, though Selkie declares that there's nothing to worry about as they stopped their plans.

Paranormal Liberation War Arc
By the end of March, thanks to Hawks' espionage and police investigation, the Hero Public Safety Commission discover several hideouts of the Paranormal Liberation Front - the most important being Jaku General Hospital and Gunga Mountain Villa - and organize a large force of heroes to raid both and take down the villain organization. Selkie is part of the team of heroes in charge of raiding the Gunga Mountain Villa.

Attacking by surprise, the heroes nearly overwhelmed the PLF, but the situation drastically changes when Gigantomachia springs into action to reunite with Tomura at the hospital, leaving a trail of destruction in his wake. While several heroes try to stop the hulking beast, the rest face the PLF soldiers. Selkie prepares to help fight Re-Destro.