Arifureta Shokugyou de Sekai Saikyou

Synopsis

A slavery gang captures a rare mermaid child named Myu and decide to sell her. Hajime returns Will to his father and collects his fee. Deciding they need a break they explore the city as tourists. At an aquarium they meet a sentient talking fish and decide to free him. As thanks he passes on a rumour of a captured mermaid child. Deciding this bothers him Hajime and Shea wander the city until he senses the child in the sewers underground and rescues her, enraging the slavers boss. Hajime and Shea keep Myu safe but struggle with what to do next. Elsewhere Yue and Tio discuss sharing Hajime between them. Hajime decides to give Myu to the city guards, despite her begging to stay with Hajime. After handing a tearful Myu over the guardhouse is attacked and Myu kidnapped again. Enraged, Hajime begins systematically executing known associates of the slavers looking for the upcoming auction. saving many children along the way. Locating the auction in a noble's mansion Hajime executes the boss, rescues Myu and blows up the mansion along with the auctions customers. Myu decides to start calling an uncomfortable Hajime "Papa", which causes Yue, Shea and Tio to demand Hajime get them all pregnant with his children.

(Source: Wikipedia)