Wikipedia
Takeminakata-no-kami or Takeminakata-no-mikoto , a.k.a. Suwa Myojin is a Shinto deity associated with warfare.
In the Kojiki, Takeminakata is portrayed as the son of Ōkuninushi, the earthly deity of Izumo province. When the heavenly deities sent Takemikazuchi to conquer Izumo, Takeminakata's brother Kotoshironushi acceded to the heavenly gods' demands and surrendered. However Takeminakata himself then appeared, carrying an enormous rock on the fingers of one hand, and insisted on a test of strength with the newcomer. When he tried to seize Takemikazuchi's hand, the latter turned his hand into a sword, but when Takemikazuchi grasped Takeminakata's hand in return, he was able to crush it like a reed. This contest is regarded as the first example of sumo.
Takeminakata fled to Suwa, where he surrendered to the heavenly deities. Some oral traditions relate that Takeminakata fought and defeated the mountain god Moreya-no-kami in order to enter Suwa, using a wisteria vine as a weapon. Takeminakata subsequently became the principal deity of the Suwa shrine. A natural ice phenomenon of Lake Suwa is explained in Shinto mythology as being caused by Takeminakata leaving the shrine and crossing the lake to visit his spouse Yasakatome, who is enshrined on the opposite shore.