Natsumi Seto

Natsumi Seto is the heroine of Heroes of the Sea Lifesavers. She is Souya's childhood friend. She's good at cooking but bad at swimming. She can't swim for 10 years since she nearly drowned while she was on a boat with Souya at the sea. She made an apperance in Hayate no Gotoku! Chapter 75 and Chapter 359, But had no involvement in the main story. (Source: Hayate no Gotoku! Wikia)