One Punch Man, Vol. 5

One. One Punch Man, Vol. 5. 216. 206p. ISBN 9781421569543. 

At the end of One Punch Man, Vol. 4, Saitama and Genos were rushing to protect city from the Deep Sea King. On location, many heroes gather to fight the Sea King, but even Class S heroes find themselves unable to defeat him and lose their lives. Wishing to kill as many people as possible, the Sea King breaks through a supposedly safe refuge. Class C heroes step up and confront the Sea King, but they are also defeated. 

Puri-Puri Prisoner, who had escaped from the maximum security prison to fight against the Sea King puts up a valiant fight, but he too is taken down by the Sea King. Speed of Sound Sonic, who had escaped with Puri-Puri Prisoner, barely escapes with his life. Genos, who reaches the monster before Saitama, engages in combat, but despite all of his best efforts he is almost destroyed, and ends up laying in ruins on the ground. Saitama finally arrives, and quickly defeats the Sea King with one punch, but to Genos' dismay he owns the people turning against him. But not all is lost, as Saitama begins to receive thank you notes in the mail ...

The story continues in One Punch Man, Vol. 6.