Spoiler Summary [Click to show or hide]:
OPM Manga Chapter 8.5 goes a little sidetracked showcasing the young Saitama when he was 12 years old in junior high…
He was then a normal kid in his school uniform with no superpower and the hair intact.
There was nothing special about him except that he was bullied, forgot his homework, and reprimanded by his teacher.
One special thing though was that he chased a monster called Piggy Bank trying to get back his 200 yen.
He never got his money back but the monster knocked him down unconscious.
A few panels later, he was seen walking in a snowy setting with a kind sitting on his shoulders. They were talking when a huge snowman monster appeared and threatened to attack them
The kid asked if he could beat the monster to which our manga hero reassuringly said yes.
Unfortunately, it’s garbage day and he forgot to take out the trash!