Saitama as Genos's Protector

Several months ago, I read a comment (somewhere) that suggested that Genos coming along prevented Saitama from falling too far down the apathy rabbit hole. 

This is certainly true! One of my favorite scenes from the initial manga volumes and Season 1 of the anime is the "training session" in which Saitama refrains from punching Genos, then knuckles his forehead ("I'm hungry--let's get something to eat"). He may not have wanted a disciple--or a roommate--but contact with Genos brought Saitama into the Hero Association and has given him various reasons (other than "where is all that noise coming from?") to investigate and help out others. If nothing else, contact with Genos fills Saitama's day!

However, Volume 25 confirms the other side of the equation: Saitama has saved Genos. 

Take Genos's situation. Orphaned; obsessed with his mission; almost deliberately recruited by the Hero Association (they wait for Genos to apply but those scenes imply that reaching out to Genos was only a matter of time) yet also distrusted and misused; on his own at age 19 except for an aging and increasingly concerned doctor--Genos is, unfortunately, almost the perfect patsy.

Give him a strong enough authority figure, like Metal Knight, and he might just have followed along in the other's footsteps. 

Dr. Kuseno checks out Saitama for exactly these reasons: he wants someone kind and non-nefarious to look out for this terminally self-destructing young man. 

Saitama's "que sera sera" philosophy is Genos's salvation. He doesn't try to mentor Genos since he feels entirely inadequate on that score. He rarely interferes in Genos's business. He rescues Genos on occasion but only after Genos has gone as far as he can. He follows Genos's lead with only minimal complaints. He focuses Genos on the mundane and day-to-day, like a sale at the local market.

Consider that Superman and Batman--a strong angst-filled relationship!--are almost constantly interfering in each other's "important" business since their philosophies and personalities create automatic tension. They can't leave well enough alone.

Saitama leaves Genos to be Genos. The result is that Saitama does not take advantage of Genos.

Consequently, in Volume 25, Genos can tell the powers-that-be with utter confidence and of his own volition, "I will not take orders. I follow someone else."