Masaru is a cheerful, hot-headed showoff and seems to be the one who has a more goofy outlook on life. He is extremely energetic and constantly brags about his role as the Hero and leader of the Warriors of Hope, despite the circumstances of how he became "leader" (by winning in Rock, Paper, Scissors).

He loves praise and fame. He refers to himself using orecchi, a form of the Japanese pronoun ore, which can be rude depending on its context but is often used when a speaker wants to assert a feeling of superiority. He also calls himself "Lord Masaru Daimon".

He is also very playful, naughty and mischievous in nature. He likes to boss around others due to his role as the leader and seems to enjoy pranks. For example, he once locked Jataro Kemuri in the bathroom. However, he is always very considerate and respectful towards Monaca Towa.

Masaru has been described as "bratty" and an "idiot". He seems to have a childish "boys are better than girls" way of thinking, as he thinks that girls are stupid and cowardly. Both Monaca and Kotoko call him perverted, though a line in Ultra Despair Hagakure implies that he's still very naive and doesn't really understand sexual things. He is one of the more child-like and less intelligent members of the group, enjoying very childish jokes and being completely unaware of what is truly going on. He also seems to have a habit of remembering certain words incorrectly.

Although Masaru is childish and arrogant, and very focused on becoming the ruler of Towa City and children's paradise, he is shown to genuinely care about the people he leads. He wants to make sure that the kids won't need to feel afraid anymore and he forces himself to be brave for them. He takes his role as the "Hero" very seriously and works hard to live up to certain hero tropes, like being fearless and never losing.

Though he usually appears very cheerful, he can get very upset and break down crying if he is reminded of his abusive past.