is an action manga written by To-Ru Zekuu and illustrated by Yuna Takanagi. It is serialized in Kodansha's shōnen manga magazine Monthly Shōnen Sirius, and has been licensed in North America by Del Rey Manga.
Story
Just before his fourteenth birthday, Akira Kizuki discovers that he is a shiki tsukai, a magical warrior with the ability to control the seasons. He is a special one called the "Shinra" He soon finds himself being protected by an attractive humanoid kijyuu named Koyomi. As shiki tsukai, they are keepers of the seasons and defend them against the evil forces that threaten to destroy the delicate balance of the natural order. Now spring and winter Shiki Tsukai fight against summer and fall to protect the human race.
Terminology
Shinra Banshou
The Law of the Universe
Shinra
One who is loved by the seasons and can use all Shikifu in existence and can cease the battles, however the power is too much for Akira to use and winds up controlling him. A forced awakening will cause him to destroy everything. Shikifu Cards that embodies the power of the season and month of those who use them, they typically appear in locations with matching temperature. A Shiki Tsukai can only use one corresponding to their birthday. They are created by Kijyuu or given birth by women. One Shikifu can absorb another adding more Sigil dates, making it more powerful, this is called inclusion. The shikifu of the Shinra Banshou can use every incantation. Sigil Dates The points on the Shikifu that represent dates, certain ones are needed to cast certain spells. The more dates a card has the more powerful it is. Shiki Tsukai Those who can use Shikifu, they are the keepers of the seasons that exist to bring the seasons back to their regular pattern. All men Shiki Tsukai inherit Shikifu, while women can create them. Those who create Shikifu can never give birth and many have been driven insane by it. Shiki Tsukai also age slower than normal humans and live longer, explaining why they look so young, if born on a leap year they only age once in 4 years. They also mentally mature faster than normal humans. Kijyuu Kijyuu are born from nature and are an embodiment of nature themselves and protect the earth. They come in multiple forms and they instinctively fight against humans, who have been destroying its master, the earth.. When defeated they become shikifu as a sign of submission. They do have a will of their own and so far only two humanoid(amalgamated) types have been revealed Formation A sealed dimension set in place using a Shikifu it acts not only as a means to hide from ordinary people but can be spread out depending on the Shikifu to cover the entire country if needed. Inside a formation of the corresponding season, spells powers increase and you can detect other Shiki Tsukai and Kijyuu. A stronger Shiki Tsukai can overwrite a weaker formation.