One Punch Man, Vol. 2

 One. One Punch Man, Vol. 2. 2015. 199p. ISBN 9781421585642. 

Now that Saitama has accepted Genos as his apprentice following the events of One Punch Man, Vol. 1, the two of them settle into normal live, with Genos still trying to figure out Saitama's secret for becoming so strong. With the evil genius responsible for the attack on their city still on the loose, they decide to take the fight to the House of Evolution instead of waiting for the next surprise. 

Deep in this secret underground lair, Saitama and Genos encounter Carnage Kabuto. After being baited by Carnage Kabuto, Saitama reveals that his secret for becoming so strong lays in ... exercise. Lots and lots of exercises. Both Genos and Carnage Kabuto are incredulous. There's got to be more! The fight is resolved quickly when Saitama discovers that today is in fact the bargain day at the store that he's been waiting for.

Meanwhile, the Paradisers are rampaging through town, and though Saitama decides to intervene, he is confronted by Speed-O'-Sound Sonic, but a well-placed hit to the groin slows down his enthusiasm for the fight, and he withdraws, vowing to defeat Saitama the next time they meet. At the same time, a nefarious organization has been collecting data on the suit that the Paradisers stole ...

The story continues in One Punch Man, Vol. 3.