Setsumatsusha

[4] The practice of building sessha and massha shrines within a jinja predates written history.

The earliest setsumatsusha usually had some strong connection to the history of the area or the family of the enshrined kami.

[5] From the Japanese Middle Ages onwards, at other shrines popular kami like Hachiman, Inari or Gozu Tennō (牛頭天王) were often enshrined[note 2] in setsumatsusha, but no clear distinction between the two terms was made.

[5] When the shakaku (社格) shrine ranking system was abolished in 1946, legally the distinction disappeared, but both terms remained in use out of habit.

It owes its name to the fact that, unlike other shrine styles, it doesn't feature a stairway at its entrance, and the veranda is completely flat.