[1] Seki Castle is located in the Sekitate neighborhood of the southern end of Chikusei City.

Kitabatake Chikafusa, who wrote an impassioned letter to Yūki Chikatomo based at Shirakawa Castle for assistance, managed to escape the disaster.

[2] At present, the site of the castle is mostly under private houses and paddy fields, but fragmentary ruins of earthworks and empty moats remain in various places.

Traces of a pier in the swamp on the lower west side have also been found, indicating that primary access to the castle, for at least part of the year, was by boat.

[2] The castle site is about a 20-minute walk from Tobanoe Station on the Kantō Railway Jōsō Line.