セブンオーシャン

Nanami Sekai gets scammed out of every penny he has, left only with a pair of boxers and a 3,000,000 yen debt. He then meets a girl, Ritori, who offers him a deal that seems to good to be true: she will take care of his debt if he will be her captain and help her with her job.

[Note] It seems that this manga has been discontinued because the author became incapacitated during serialization and was not able to keep 2 series running.