The circle indicate the time we discuss in this section
The Heian period is the time when the shape of the swords changed to the present curved shape. Until then, swords were straight. It is a commonly accepted idea that the study of swords begins from the Heian period. Swords before the Heian period are in the category of archaeology. The main reason for that is the sword-making technique saw a significant improvement after the Heian period.
The elegant, graceful lifestyle and the Heian culture then were reflected upon the swords’ style. A group of swordsmiths in the Kyoto region created a particular sword style called Yamashiro Den (Yamashiro School). The shape of their swords shows a graceful line. The most famous sword of this time is Sanjo-Munechika (三条宗近, Previous chapter), a national treasure today. The style of Yamashiro Den represents Heian period swords. 
General Heian period sword style
Shape———- The length of a sword is approximately 30 inches ± a few inches. It has an elegant and graceful form with a narrow blade and a small kissaki(小切先). The curvature is deep. This style is called Kyo-zori (京反り) or Torii-zori (鳥居ぞり). With the Kyo-zori style, the deepest part of the curvature comes around the halfway of the blade. The lower part of the sword flares out, making an A-line shape like the lower part of the Eiffel Tower. This flaring shape is called funbari (踏ん張り).
Hamon(刃文)———- Hamon is the line that was created when the sword was tempered. The Hamon on the Heian period swords is narrow and usually Suguha (直刃). Suguha means a straight line. The Hamon is also Nie-base. Nie(沸) is a tiny particle in the Hamon. As shown below, if you look closely, you will see fine sand-like particles in the Hamon line.
Ji-hada (地鉄) ——– Fine wood-grained pattern. The location of Ji-hada (or Ji-tetsu) is between Hamon and Shinogi (see 3 |Names of Parts)
Nakago (中心)———- Nakago is a hilt area. Sword makers inscribe his names here. The shape of the Nakago during the Heian period is often Kijimomo shape(雉腿), which means pheasant thigh shape.
Hi and engrave ———- Hi (樋) means an engraved straight line. Hi and other engraved designs are rare during the Heian period. These became more common later time.
Kissaki (切先）———– The Heian sword’s kissaki is Ko-gissaki, meaning small kissaki. The Hamon line on the Kissaki is called Boshi. In this period, the type of Boshi design is called Komaru, meaning small, round, and wrapping the tip.
Names of the Heian period swordsmiths
- Yamashiro school——– Sanjo Munechika(三条宗近) Sanjo Yoshiie(三条吉家） Gojo Kanenaga(五条兼長) Gojo Kuninaga (五条国永)
- Yamato school ————-Senju-in (千手院)
- Bizen school ————— Bizen Tomonari(備前友成) Bizen Masatsune(備前正恒) Bizen Kanehira (備前包平)
- Hoki (伯耆) —————–Yasutsuna (安綱) Sanemori (真守)
- Buzen (豊前) ————– Cho-en (長円) Sinsoku (神息)
- Satsuma (薩摩) ————Naminohira (波平)
Study of Japanese Sword 