Hyakkimaru is a slim, pale youth with a pair of dark brown prosthetic eyes. He has long black hair that is tied up to a ponytail and bangs that pass his chin, often covering parts of his emotionless face. Like his mother, Hyakkimaru also has thin eyebrows.
He wears a long scarf along with a tattered cloak during his travels. Underneath is a worn, black kimono with many white ancor-shaped patterns and a strip of white cloth tied on his waist. He had many bandages wrapped around his body and a sheath equipped on him.
Not much of his personality was revealed as he is unable to express himself due to the lack of certain features.
However due to the limited access he has to the world, he is naive and sensitive to his surroundings. Due to being blind, he is calm and level-head. He is fearless and brave to fight and kill monsters and demons.
However, after Mio's death, his emotion is unable controllable as he was consumed with rage and killing Kagemitsu's troops who killed Mio and the orphaned children implying he can be a monster until Dororo calmed him down. When seeing the same man who killed Mio, Hyakkimaru attempted to kill him but Dororo tries to stop him.
In 1969, Hyakkimaru avenged his mother's death when after killing the 48 demons and his father, Kagemitsu Daigo. In 2019 when being called Son by his mother, Nui No Kata, Hyakkimaru seemed happy knowing that his mother loves him in return, he hold a great love for her. However, he was horrified when his mother stabbed herself for her forgiveness to her son. Learning about truth of his father's greediness, Hyakkimaru now seeks to end his mother's suffering by killing his father, Kagemitsu Daigo.
In 2019 series, After learning truth of his father's evil nature from his mother, Hyakkimaru held a greatest hatred toward his father who became his archenemy as he will never forgive him as well to kill him for cursing him and disrespecting and abusing his mother. Hyakkimaru refused to acknowledge Kagemitsu and killed his father without hesitations. After killed all the demons, Hyakkimaru decided to kill his father to get back all of his body parts.
He has a sibling rivalry between him and his younger brother, Tahomaru due to Hyakkimaru got attentions and being loved deeply by his mother, while Tahomaru wasn't able to giving his attention to her at all. He feels guilt after he killed his brother. In 2019, He has no regrets of defeating his brother when he was deceived by their father's manipulations and deceptions as a result as he didn't hesitated or regretted of slashing Tahomaru's right eye.
His goals are to kill the demons who took his body parts and to kill his power-hungry father, Kagemitsu Daigo and kill his own brother, Tahomaru since under Kagemitsu's deception. In 2019, he gave up of attempting to kill them as they died by themselves.
- In 1969 after regain his voice, he speaks normally. In 2019, he speak slowly after regain his voice.
- Hyakkimaru is similar to Sesshomaru from Inuyasha.
- Hyakkimaru has similarity of Jin Kazama from Tekken as they fight and betrayed their own family members and attend to end the cursed bloodlines by killing their own fathers. Hyakkimaru has some similarity of Kazuya Mishima as their desires to kill their fathers for killing their love and show no mercy like a devil (Kazuya's mother, Kazumi was killed by Heihachi and Hyakkimaru's lover, Mio was killed by troops under the order of Kagemitsu Daigo and did bad things to them in their youth, Hyakkimaru was abandoned by Kagemitsu and Kazuya was tossed into the cliff by Heihachi). They both possessed the power that of a devil.
- Hyakkimaru's appearance is similar to Naruto Shippudens secondary villain, Madara Uchiha or possibly the incarnation of Madara.
- Hyakkimaru's ponytail is similar to Haohmaru from Samurai Shodown.
- Hyakkimaru is assumed to be very first main protagonist and anti-hero of the first series.