Daimon is a type of Japanese kimono for males.
Around the Kamakura period, it became fashionable to put large patterns on Hitatare (a kind of court dress in old days). In the Muromachi period, that sort of kimono was called Daimon to be distinguished from Hitatare. In the late Muromachi period, Daimon was made of linen with its pattern on a fixed position and was considered as the second formal wear, following Hitatare.
In the Edo period, Edo bakufu (Japanese feudal government headed by a shogun) defined Daimon as 'a formal wear for samurai families with Buke-kani (official court titles for samurai) or higher titles.'
In those days, ordinary daimyos were customarily appointed to the Fifth Rank, so Daimon became a formal wear for daimyos. Both the upper and lower parts of Daimon at that time were made from the same material, and the lower part, hakama, was so long that the wearers had to drag it. There was a big difference between Daimon and Hitatare or Suo: family crests were dyed out at ten parts of Daimon, including larger family crests at the back, right and left front sides, back side of each sleeve, and the backside of the hakama and smaller crests at two places on the front part of the hakama.
At present, we can see Yasuie TOGASHI wearing Daimon in 'Kanjincho' (Kabuki (traditional performing art)) and Naganori ASANO wearing one during the scene of 'matsu no roka' (literally, a corridor of pine trees) in 'Chushingura' (period drama). Thus, Daimon is now used only for stage garments.