Spoiler Summary [Click to show or hide]:
OPM Manga Chapter 19 shows Saitama and Sonic face in the middle of a busy street, and Sonic quickly attacks him with a swift slash…
Saitama bites his blade and shatters it, leaving Sonic baffled. He doesn’t want to fight Sonic because he’s looking for monsters and bad guys.
Tank Top Tiger approaches both of them because he thinks Saitama looks suspicious. After intimidating Saitama, knowing he’s Class C and he’s at Class A, he mocks him to get more attention.
Sonic interrupts by knocking Tank Top Tiger with his exploding shuriken. He then indiscriminately attacks everything and everyone around to force our One Punch Hero into a fight.
After realizing that Sonic was the bad guy he was looking for, Saitama hand-chopped Sonic from behind, knocking him flat on his face.