Eye of Tomonori

The Eye of Tomonori (トモノリの目 Tomonori no Me) is an artificial eye owned by Jubei that is hidden underneath his eyepatch. It was created by Rachel Alucard and is based on the eyes of Tomonori, its namesake. It allows its user to see the true form of Yuuki Terumi.

Information
Before the final battle against the Black Beast during the Dark War, Jubei asked for the Hihiirokane from Rachel Alucard in order to open up a pathway into the Beast for Celica A. Mercury and the Deus Machina: Nirvana. She gave it to him on the condition that he use it in conjunction with the Eye of Tomonori to kill Terumi. Jubei was already missing his right eye from a fight against a Remnant of the Beast, and so the Eye of Tomonori functioned as its replacement. Jubei was only able to use the Eye once during a fight against Terumi some years after the war ended. He did have Hihiirokane with him at the time, so was unable to land a killing blow.

Rachel developed the Eye using the real eyes of Tomonori. Tomonori managed to see Terumi's true spirit form in a battle against him and Kazuma Kval at the Lost Gate. Tomonori was killed during this fight and his corpse presumably retrieved by Valkenhayn R. Hellsing. In 2200, the Eye was handed by Jubei to Platinum the Trinity. As Tomonori had spent time with Hihiirokane, the Eye was able to be used to create a replica of the weapon with the Nox Nyctores - Arma Reboare: Muchourin. It is unknown if they returned the Eye back to Jubei afterwards.

The pupil of the eye is red with a pink ring around the center. When activated, the ring turns a bright yellow and an ornate design forms around Jubei's eye, cheeks, and forehead. He can take out the eye at any point.

Trivia

 * The eye is referred to both as the Eye of Tomonori, as well as Tomonori's Artificial Eye (トモノリの義眼 Tomonori no Gigan) throughout Phase Shift 4.
 * An activation call was used only in Hakumen's Continuum Shift story mode, referring to it as the Sekigan. The activation call used was "Edify this sight, Oh single eye of mine" (啓け我が隻眼！ Hirake Waga Sekigan!) in Japanese, but simply "Sekigan OPEN!" in the English script for the game. This is the only known use of Sekigan as a name for this eye, and subsequently released materials simply refer to it as the Eye of Tomonori.