Maseo Yamashiro

Maseo Yamashiro, played by Karl Yune, is a man from Oliver's past who returns in his present.

Maseo joins the League of Assassins and is on the side of Ra's al Ghul, but still has a soft spot for Oliver considering their history. After Oliver is beaten by Ra's, Maseo takes him to Tatsu, who heals him. Maseo cannot be convinced to return to Starling City with his friend, even though he'll be facing consequences if Ra's finds out about what he's done. He even kills a couple of assassins himself when they find the hideout.

Maseo finds it to be a very bad decision for Oliver to turn down Ra's al Ghul's offer to take his place. He warns him that it won't go over well with the man, but Ollie still declines. Ra's sends assassins to impersonate the Arrow and turn the city against him. Maseo ends up shooting an arrow through the mayor's torso to help the facade.

After Thea is hurt, Maseo waits for Oliver to show up. When he does, Maseo tells him that if he accepts the offer to become the next Ra's al Ghul, the current Ra's will help bring Thea back. In Nanda Parbat, Maseo talks to Diggle, trying to explain the situation. He mentions losing his son and how that changed him, and Diggle wonders if Akio would be proud of his father. This resonates with Maseo, who then tries to help Oliver escape. When Ra's asks Oliver who the traitor is, he won't say, but Maseo immediately confesses. Ra's recognizes that he let his old life creep into his current one, and spares him.

When Oliver offers to free Maseo from the League when he becomes the new Ra's, Maseo thanks him for the sentiment but tells him that Oliver can't release him from his prison. When Tatsu shows up with the rest of Ollie's friends, Maseo attacks her. She gets the better of him and lands the killing blow. He lies in her arms as he dies, and thanks her for freeing him from his prison.

Season 3 Flashbacks

Maseo is living in Hong Kong and is forced to work for Amanda Waller after having his wife and son threatened. He works in conjunction with Oliver Queen. When Tommy Merlyn shows up to find Oliver, Maseo helps Ollie turn Tommy back so that he won’t have to be killed.

Maseo and Oliver are tasked with tracking down China White. Waller calls Maseo with a lead on Li Kuan Hui and Maseo follows it up but his wife, Tatsu Yamashiro is worried when he doesn't check in after nine hours. Ollie goes to where Maseo went and gets knocked out. Tatsu helps Oliver by wielding a sword and getting information from one of the men, who says that her husband and a few others are dead. However, when they get back home, they discover that Maseo is fine.

Maseo tells Oliver that it was necessary to torture a man when Ollie feels guilty about it. The two of them infiltrate the lab to steal a sample of the virus and they find that it's already been taken. They torture the man who stole it but he won't give up any info. Maseo tells Oliver about a plant that basically allows someone to be brainwashed.

After Tatsu is taken by China White, Waller tells Oliver and Maseo that they need to steal Alpha, which goes along with Omega. They manage to do so, but Waller is pissed that Oliver didn't capture anyone so that they could torture him for information. However, Ollie reveals to Maseo that he put a GPS in the guy's pocket so that they could track him down in order to find Maseo's wife.

Oliver and Maseo meet with China White, and Maseo says he has the Alpha and will give it to her in exchange for Tatsu. However, it turns out to be a fake, and Oliver, Maseo, and Tatsu have to fight their way out. Maseo admits later that he really did have the Alpha sample but that Waller must have switched it out at some point, knowing he'd pull this move.

Maseo and his family leave Hong Kong and he tells Oliver to disappear as well so that Waller can't find any of them. Ollie places a call to his mom, as Maseo instructs him to, in order to make it more difficult for Waller to kill him, although it doesn't work.

Maseo comes back for Oliver, saying that he lied about their destination in the first place, figuring Ollie would be tortured. Waller takes both Oliver and Maseo back to Starling City. Maseo and Oliver track Peter Kang, someone who works at Queen Consolidated, so that he'll lead them to China White.

Oliver then refuses to go with Maseo to complete the mission at first, but Oliver shows up and saves him when Maseo is about to die. Oliver, Maseo, and Tatsu are told by an army general that they are now free, and that Waller is no longer involved. However, on the way to the boat that will take them home, they're attacked. They're forced to split up and Maseo and Tatsu make sure that Oliver grabs their son, Akio.

After a little while, they're all able to meet back up. When Ollie tells them to get out of Hong Kong, they refuse to let Ollie handle everything on his own. Together, they go after the Omega and Alpha viruses. The virus is accidentally released, and Akio shows signs of having it. Maseo and Oliver immediately infiltrate the nearby army base and find Shrieve there. Maseo shoots him in the arm to get him to tell them where the cure is. They take both the cure and Shrieve back to where Tatsu and Akio are, but it's too late, and Akio has died in Tatsu's arms. Shrieve reveals that there isn't a cure, anyway, and they're surrounded by his men.

Maseo and Tatsu mourn the death of their son. They have him cremated and each take an urn, and Tatsu gives one to Oliver. Oliver then takes to torturing Shrieve, which Tatsu finds appalling. Maseo puts him out of his misery by shooting him dead. He then tells Tatsu that he can't be with her because she reminds him of Akio, and because he is undeserving of her love. He leaves her, Oliver, and the city behind.