|Birth date:||March 16 (Pisces)|
|Personality:||Regal, Dignified, Curious|
|Emblem Frame:||Papillon Chaser (RA-006)|
|Rank:||Second Lieutenant (TCY 417)|
|Theme Song:||Fureru Nara Sotto|
- "I said that I had taken a liking to you, had I not?"
- — Natsume Izayoi —
Natsume Izayoi (ナツメ・イザヨイ?) is the sixth female member of the Rune Angel Troupe and she pilots Papillon Chaser. She was the duchess of the Seldor Alliance unaffiliated Arms Alliance, and believed that both Seldor and EDEN were incarnations of evil.
Natsume is introduced early in the conflict between the Luxiole's crew and the Arms Alliance and was technically the first "member" of it to face the Rune Angel Wing. In an attempt to dispense "justice" Natsume faces the Luxiole with a small amount of ships and her Papillon Chaser. She is promptly defeated and is taken aboard the Luxiole as a "captive". Kazuya is assigned to keep watch over her and while Natsume is not too eager to befriend others, she slowly begins to warm up to the crew.
It would not be until the transmission with Genivres that Natsume realizes that she has been left behind for good and that her authority in the Arms Alliance is completely null and void. Natsume begins to side with the Luxiole's crew and aids them by giving Benedictine's fleet formations stationed at the planet Pico. She would join the fight against her former allies at Seldar when her Emblem Frame is finally repaired.
Natsume's route is only implemented in Mugen Kairo no Kagi's 2nd Disc when it all other routes, she only assists in the route conflict and partakes in the penultimate fights. Natsume's route conflict begins where in order to bridge the relationship between the Seldar Alliance and the Arms Alliance after the misdeeds of the Three Marquis, would be for Natsume marrying into Seldar's Royal family. Kazuya is against this and for speaking out at the wedding, he is incarcerated.
The Rune Angel Wing, with the exception of Roselle, agreed with Kazuya's intentions and decide to break him out of his captivity and have Kazuya and Natsume stake out on a nearby moon to wait things out. Kazuya and Natsume spend some time together but Kazuya eventually gets ridden with an illness and for their best interests, they return to the Luxiole. Coincidentally, the White Moon is pulled through the Infinite Corridor into NEUE and the political marriage is stopped.
Within the Infinite Corridor, Natsume would have one last conversation with her former caretaker.
- Similar to Chitose, Natsume's romantic relationship with Kazuya takes root in the second game but is not realized until the last game in their respective trilogies.
- Natsume makes her full appearance in the Rune anime while also making a cameo in Kazuya's ending in ZRnT acting as a "spy" at the planet Magic.
- In the post-game omake of Eigou Kaiki no Toki, Natsume reveals that she has 4 younger siblings.
- Natsume is voiced by Atsuko Enomoto.
- Natsume's name comes from the Japanese name for the Jujube fruit, a fruit which is used in the production of some confectioneries.