Shizumaru Hisame (緋雨 閑丸, Hisame Shizumaru) is the main protagonist and one of the new characters in Samurai Shodown III. He continues to appear in other titles of the series.
Although he was initially believed to be based on Kenshin Himura (the main protagonist of the manga/anime series Rurouni Kenshin), creators state that his visual model was based on Kurama from the manga/anime series YuYu Hakusho.
According to Gamest Mook, he was one of the potential candidates for the Samurai Shodown 64 lineup but was taken out due to time and modeling constraints concerning the low polygon count and difficulty of recreating his umbrella. In their 1997 Hero's Collection, Gamest staff voted him as their thirteenth favorite character (tied with King of Fighters character, Benimaru Nikaido, for the same spot). In the Neo Geo Freak's 1997 Volume 8 character poll, he was voted as the ninth favourite character with a total of 1,072 votes. 
He is a young amnesic boy who doesn't remember his real name (he named himself after his sword). Because he was deemed a "demon's child" since childhood, he lives and survives alone. He travels to find a "demon", hoping to figure out for himself what it means to be one. 
During the events of Samurai Shodown V, he was taken in as a servant by a noble young couple. The husband leaves to fight in the war at Hinowa, leaving his wife, Hakana, under Shizumaru's protection. Pregnant, Hakana wants to return to her father (who Shizumaru doesn't know is Youkai Kusaregedo) for shelter. Shizumaru, assured she is safe, feels obligated to help in the war. When the battles are over, he is rewarded a hefty sum of gold for his efforts. He leaves for home but is stopped by a man who calls him Yaiba (刃, Yaiba). Despite Shizumaru's denial, the man insists that he is Yaiba and that "his family" misses him. Shizumaru chooses to stay with his master and flees. Unfortunately, his master dies in the war and Hakana is eaten by her father. Due to the trauma he has suffered, he labels anything malicious, be it person or mannerisms, as a "demon".
He respects Haohmaru, who inspires him and teaches him the philosophy of the sword at an early age. Shizumaru seeks to defeat Zankuro and supposedly avenge his family's death. He slays Zankuro.  After the events of Samurai Shodown IV, he confuses the remaining blood lust within him as a "rampaging demon". However, he comes to accept his "demon" as a natural part of himself and makes peace with his past.
In the NeoGeo CD version of Shinsetsu Samurai Spirits: Bushidou Retsuden, he stars in the bonus portion of the game with his own story. It is essentially a choose-your-own-adventure on how he should find Zankuro.
Although there is speculation that he is related to Zankuro, this claim is also dubious. Developers from Samurai Shodown III state that they are not related. By contrast, the staff in Samurai Shodown V state that Shizumaru's real name is Jin Minazuki (水無 月, Minazuki Jin). It's still unconfirmed if Yaiba and Jin are really Shizumaru.
For a boy his age, Shizumaru is quiet and timid. He is a polite, well-meaning child who tries to warn others about the "demon" within him. He tends to label things that are unknown or bad to him as evil demons, convinced that they are real. Due to his subconscious belief of himself being a demon, others have started sensing a comparable malevolent aura in him, and even his own moves subtly hint at this, suggesting Shizumaru isn't just paranoid about it.
- Reflector - Shizumaru can reflect a projectile back to its sender.
His fighting style is an unique combination between his umbrella and his sword. When he first premiered, he relies on his umbrella more, using his sword occasionally in special moves. His latter appearances, however, have him using more sword techniques, minimizing his umbrella attacks. His move set incorporates an uppercut move similar to Haohmaru's Kougetstuzan.
A vision of Zankuro will appear in his Zetsumei Ougi in V Special.
- Kazu Kaoru (Aroma of the Wind) - Samurai Shodown III
- Tsubana-Nagashi - Samurai Shodown (2019)
- Samurai Shodown III
- Shinsetsu Samurai Spirits: Bushidou Retsuden (Neo-Geo CD version only)
- Samurai Shodown IV
- Samurai Shodown!
- Samurai Shodown V
- Samurai Shodown V Special
- Samurai Shodown VI
- Samurai Shodown (2019) - DLC character
- Kingdom Story
- Samurai Shodown Tenkadaiichi Kenkakuden
- Samurai Shodown: Oborozuki Densetsu
- SNK Fighting AGE
- If the characters in his last name are broken down into basic components, his name becomes "rain of blood" (血の雨, chi no ame). Creators confirm that this was intentional. In the short drama found on the Samurai Shodown best CD, he says that he was named after the name engraved on his sword, Shizu. The backstory for Samurai Shodown III says that a monk called him Shizuka (閑) due to his quiet nature.
- Also in his Special Move in Samurai Shodown (2019), occurs a rain of blood, the exact meaning of his name.
- When asked "The path of the sword is?", Shizumaru's response is "Something that might come in handy one day." 
- He was one of the veteran characters from the series who didn't receive a re-dub in the anthology version of Samurai Shodown VI.