|This article is about a/an ally in Kamen Rider Decade.|
Natsumi Hikari (光 夏海 Hikari Natsumi) is one of the few last surviving humans in the World of Negatives. She confronts her prime counterpart in an attempt to warn her of Otoya's scheme, only to be forced to dig up the K-Touch she had hidden. She eventually gives her goodbyes to Natsumi while entrusting the K-Touch to Tsukasa, remaining in her world out of hope for the future.
Behind the scenes
Natsumi Hikari was portrayed by Kanna Mori (森 カンナ Mori Kanna).