Sweet Mask has a generally low opinion of Genos. He converses with Genos after the latter is admitted directly into the S-Class without Sweet Mask's approval, a fact that bothered him, but after seeing that the cyborg seemingly matches up with his view of heroes, he accepted it nonetheless. He speaks to Genos a second time after the Dark Matter Thieves are defeated, calling Genos a "disappointment" (referencing his defeat by the Deep Sea King and his inability to assist against the alien threat). However, Genos did not seemed to be bothered by Sweet Mask's comments and also noticed that they have similarities.
Sweet Mask respects King for what he claims as "actually pulling his weight as a S-Class hero." Sweet Mask felt strongly enough about it to stop arguing with Flashy Flash when King entered the room.
Sweet Mask easily antagonizes Flashy Flash, almost to the point of physical confrontation. As with most of the other S-Class heroes, Sweet Mask believes himself superior to Flashy Flash.
Flashy Flash does not like Sweet Mask's authoritative and egotistical attitude. While he has some disdain towards some of the S-Class heroes, the tone he gives off is either of annoyance or even teasing, as seen with his interactions with Metal Bat. Flash's displeasure towards Sweet Mask goes to the point of eliciting his murderous intent towards the fellow hero. He goes out of his way to instigate a challenge against Sweet Mask.
Sweet Mask mockingly (but accurately) calls Zombieman a monster, calling into question his inhuman regeneration abilities and mysterious past. Zombieman is annoyed by Mask, but maintains his cool.
While he looks down on most heroes, he respects Feather, saying he has star potential.
When first hearing mention of him after Saitama killed the Sea King, Mr. Mask's opinion relegates the newbie as having the aura of a B-Class hero, based on appearances via the video feed alone. After watching the footage of Saitama defeating Sea King, Sweet Mask begin to have a minor interest in the caped bald hero's tremendous strength, thus allowing to rank Saitama up to B-class.
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After witnessing Saitama defeat Garou, however, not only does Sweet Mask fully acknowledge Saitama's tremendous strength, but becomes somewhat obsessed with him, considering him to possess the true beauty of overwhelming power and would even start to compare new heroes with Saitama, even starting a new hero project that would feature the bald hero. Despite his admiration for Saitama, he showed great displeasure for his refusal to kill Garou and lectured the hero for it.
After Sweet Mask told Saitama his origins, Saitama lectured him that appearances and origins don't matter, nor does the public opinion, and that how you view yourself is more important. When a monster known as Pesky Clown attacks the citizens and fights Sweet Mask singlehandedly, the monster becomes too powerful for Sweet Mask to fight in his human form. The hero realizes he must transform into his monster state, and after briefly going over what that would mean, Sweet Mask finally takes Saitama’s advice at heart, sacrificing his handsome appearance to defeat the monster and restart his new heroic life.