Mitsuki and Masaru only make their debuts after the Hideout Raid, when Eraserhead makes his stops at Class 1-A’s houses to gain confirmation for the students to continue attending U.A, and to stay in the 1-A Heights dorms.
The family is shown to have a rather intense- and tiring dynamic, according not only to Eraserhead, but the ever-so-patient All Might as well. At one point, the family was described to be unstable, although it is unclear if this is really true, due to Masaru and Mitsuki not making any appearances past their debut, and Katsuki not speaking about his home-life often, similar to the rest of his classmates.
Katsuki seems to have gotten all but few attributes from his mother, from her spikey blonde hair, to her sharp red eyes- the only features he seems to have gotten from Masaru are a slight tan in his skin, and a slightly darker hair tone than Mitsuki.
Mitsuki’s quirk is Glycerin, which she secretes from the pores of her face, while Masaru’s is Oxidizing Sweat, which sweats out like typical sweat, but can create a (weak) explosion when he pounds his hands together. While Katsuki’s Explosion seems to fare heavily from Masaru, it seems the chemical properties of Mitsuki’s Glycerin is what gave him the explosive kick for Katsuki to be as powerful as he is.
Mitsuki & Katsuki
Katsuki and Mitsuki are almost exactly alike, in both looks- and personality. Their explosive personalities, and unwillingness to back down lead to clashes between them, although it seems that Masaru makes attempts to break these up before they can become uncivil. Mitsuki seems to be very aware of her son’s inflated ego, and the praise that led to it, and hopes to see U.A take care of Katsuki, and help him reach his truest potential. Katsuki addresses his mom as “Old hag”, which evidently, due to her love of her youthful beauty, (given to her by her Glycerin quirk) annoys Mitsuki, so she calls Katsuki “Brat” in turn.
Mitsuki & Masaru
Masaru once had a desire to become a hero, but ended up finding his passion in the field of design, where he met Mitsuki. His section on his and his wife’s shared omake page says that once the two of them met, Mitsuki came onto him hard, and eventually won his heart. Additionally, Masaru has been stated to “have a thing” for strong, dominating women like Mitsuki.
Masaru & Katsuki
Katsuki and Masaru are not shown interacting too heavily, as Masaru’s docile nature is easily overrun by his wife (and son’s) temper(s). However, it seems that the two get along fairly well when Katsuki isn’t previously “triggered”. When Katsuki begins to lash out, despite being nervous to, Masaru does make an attempt to calm his son. Katsuki addresses his father as “Old man”, although Masaru simply addresses him by his name.
A few fans have speculated that (part of) the reason Katsuki pulls such awful faces/expressions is because he thinks he looks too much like his mom, which, as evident, could easily be true.
Due to Mitsuki calling Katsuki “weak” for being kidnapped, and even smacking him, the relationship between the two is not looked too fondly upon in the MHA/BNHA fandom, and Mitsuki is often written off to be abusive. On the other hand, Masaru is seen to be neglectful However, this cannot be fully determined due to Mitsuki’s lack of screen-time, and judging by Katsuki’s willingness to talk back, could easily be untrue. If Mitsuki is thought to be abusive, Masaru is often seen as neglectful, for reasons that can be deduced from one’s thinking. However, fans that see the family’s dynamic in a more positive light, Mitsuki’s spitfire attitude is instead taken to her being fiercely protective of Katsuki, while ever-docile Masaru is silently proud.
- A few of the kanji in Mitsuki (爆豪光己) and Masaru’s (まさる) names can be combined to make Katsuki.