Among the oldest of the Kyushu lineages, the Miike school (三池) takes its name from the locality of Miike in Chikugo province, where its founder, Tenta Mitsuyo (also given as Denta Mitsuyo, 光世), worked in the late period at the very threshold of the early . The members place the line at the head of an ancient Kyushu hand whose representative work is the Ōdenta of the Maeda house, counted among the Tenka-goken, the five swords ranked above all others in Japan. The school's accounts are equally plain that little of the founder's own hand survives; the signed blades that carry the Mitsuyo name from the period into the are read as the work of successors who inherited the signature rather than as the founder's own. So the name is the lineage: Mitsuyo was not one man but a succession, and the reads the designated work that descends to us as the school manner carried intact. By the period the line had begun to scatter, one branch relocating to Aki province as a dated Meitoku 2 (1391) attests, and the members note that the traditional style effectively closes with that era, little of its former character remaining into the .
In their own descriptions the members hold the Miike hand to a quiet register built on a distinctive ground. The forging is mixed with that flows conspicuously and stands somewhat, at times inclining toward -gakari, with and adhering; tighter examples settle into a dense . The members linger longest on the itself, naming it a sticky, surface soft to the eye, inclining toward a whitish tone with (and on broader blades a , tendency) rising over the steel. The temper is consistently -based: a slender on the work and a carrying or on the , all in , with , , within the edge, and in places , , and ; even where the is bright the tends to a subdued cast. The runs straight and returns in a calm , on some blades a turning to or a . The is the grand early figure, a broad of moderate with deep and , a compact at times forming an (boar's neck), while the are with and somewhat thick . Where the members locate the school's own individuality is the carving: wide, comparatively shallow run as kaki-nagashi or , often with an accompanying , and on some pieces above or in relief.
For the members read the work not by date but by manner and attesting inscription, and the discriminators are the ground and the groove rather than the temper. A measured in belongs to several traditions; a Yamashiro or keeps a clear, bright steel, whereas the Miike whitens and softens into the character, so the soft ground together with the wide shallow pulls the work back to Chikugo. Mitsuyo stands in a rare double light, a maker famous for one unrepeatable masterpiece and the head of a recognizable hand traced across three centuries. The Ōdenta, transmitted in the Maeda house, is patrimony and never offered; the Sohaya-no-tsurugi, a blade of Tokugawa Ieyasu, is kept at the Kunōzan Tōshōgū, and a at Honmyō-, with a signed in the Seikadō Bunko and a in the Tokyo National Museum. The later attestations are themselves part of the record: one carries a gold-inlaid Mitsuyo read as an authentication by such authorities as Kōchū, another a large gold-powder Miike Mitsuyo with a red valuing it at seven of gold in 1, and imperial transmission through the Katsura-no-miya family marks certain Aki-branch pieces. Most surviving work is gathered into shrines, temples, and long-standing collections, so a privately held Mitsuyo comes to market only seldom, and as a notable event when it does.