The groove, called “Hi” or “Bohi” in Japanese, has several purposes: it can make the blade lighter and more flexible, or it can help to drain the blood for instance. Minosaka offers a few custom options for the groove but of course, there is no finish available when the chosen option is "without groove".

• Hi Dome: Standard: the groove has an ogival shape and stops approximately 4 cm from the Habaki.
• Hi Dome: Kakinagashi: the groove goes on under the Habaki. It makes the blade even lighter and moves the balance of the blade further towards the Tsuka.
• Hi Saki: Shinken: this kind of finish looks like the grooves that can be found on Shinken. The tips of the grooves where they connect with the Kissaki (tip of the blade) are manually and delicately crafted so that both merge very naturally in the form of a triangle (standard groove have an ogival shape). This option is particularly good-looking.

For blade lengths of 2.3 shaku and below, the groove may come under the Habaki