Shiina is an average height and slim young man with messy silver hair and grey eyes. He is one of the rare characters seen to change his outfit on a regular basis. This ranges from female clothes (forced to wear by Yukari) to a dress resembling a military uniform to match Yukari's look.
He has a very close, sibling-like relationship with Kusano, despite the fact that his power is the natural opposite of Kusano's. Shiina dislikes violence and has expressed extreme remorse for hurting Sekirei he's defeated.He may be seen crying by the side of the Sekirei he has defeated. Shiina is also very calm in contrast to Yukari's brutality to the other Ashikabis to the point where he feels sorry for them. Later on in the story, when Shiina is forced to work for Higa, Higa stops Shiina from helping Yukari to escape by telling him that Sekireis and humans can never be together. After Yukari pushes Shiina off of her to prevent her skirt from falling off, he takes it as a sign that she really does not care for him. Shiina becomes so depressed that even when Higa and his best Sekirei are out at the third match, Shiina does not even try to escape. Shiina's feelings of inferiority to Higa make him obedient and easy to control but the bond Yukari and he share proved to be stronger and he escapes with Yukari. Shiina has said in episode 6 "To make a sekirei yours you will need noucoastioal contact, but I can do more if you like", this shows that Shiina has desperately wanted Yukari to be his Ashikabi. Yukari has also gotten Shiina to wear female clothing twice which means he's easily convinced, but this can also just be his love for her or he is terrified at the fact of being ambushed again.
Despite Shiina's kind-hearted personality, he can be merciless when the situation require it. Before engaging into a fight with Amebane, Shiina was disgust of Amebane's atrocious behaviour towards his Ashikabi.
Abilities and Powers
Shiina's powers are extremely dangerous and powerful; powerful enough to have inspired a wildfire of rumors about the merciless, god-like "Death Sekirei" (which is just an over-exaggerated version of Shiina himself). His power is most likely "Death" or "Decay", he can instantly disintegrate most forms of material including metal, wood, fabric and flesh to a limited degree. His Norito to remove the opponents Sekirei crest is "By the corpses of my contract completely rot my Ashikabi's cross!"
- Death Flower 
- World End Garden (ワールド・エンド・ガーデン, Wārudo Endo Gāden) (Norito)
- Death Garden
- Death Wings (死天使の羽, Shi tenshi no hane) (Norito)
It was mentioned by Kusano that she and Shiina were like brother and sister which is also reflected by their opposing powers of grow and decay. Shiina helped to keep Kusano's powers in check if they went out of control. Kusano also quotes without Shiina what is she gonna do. In fact Shiina can sense when Kusano has been crying and by the surroundings if she has been through the area. Shiina has also destroyed the arboretum which was made when Kusano was almost forced to emerge.
He is searching for Sekirei #108, Kusano, who he has a very close sibling-like relationship with. He met Yukari after being attacked and saved by her and some help from Homura. He shudders at the idea of almost being Mikogami Hayato's Sekirei. He thinks of Yukari like a bright shining light in his life. Due to the overwhelming power of his ability, he is called "Reaper Sekirei" (死神のセキレイ, Shinigami no Sekirei) and along with Yukari, are ironically considered the "most evil pair" in Tokyo upon reaching the Northern part of the city. Shiina and Yukari's reputation and power have become so feared that they have attracted the attention of Higa Izumi, who encountered them shortly after arriving at the North city, attempting to find the last unwinged Sekirei as he (Shiina) and Yukari were hoping it would turn out to be Kusano (which, of course, already has an Ashikabi in the form Minato) but was later revealed to be Homura. After his encounter with Tanigawa Junichi he expressed a desire that Kusano would have an Ashikabi like Minato.