Chansen,
I checked my files and have what appears to be two Nobumitsu. One has a long mei and his blades are Showa and large Seki stamped. I think he is this one:
NOBUMITSU (信光), Shōwa (昭和, 1926-1989), Fukuoka – “Chikushū-jū Sa Nobumitsu kinsaku” (筑州住左信光 謹作, “carefully made by Sa Nobumitsu from Chikuzen province”), real name Koyama Nobumitsu (小山信光), he was born on the 26th day of the second month Meiji six (明治, 1873) and studied under Fukuoka-Ishidō Koretoshi (是利), he lived in Chikuzen´s Ito (怡土), kihin-jōi (Akihide), Special Honor Seat at the 6th Shinsaku Nihontō Denrankai (新作日本刀展覧会, 1941) (see picture right)
The other. like yours, used 2 kanji mei, usually with a large gap between them. His blades are all '44 & '45 made, and are Gifu & Na stamped. This is likely your guy:
NOBUMITSU (信光), Shōwa (昭和, 1926-1989), Gifu – “Nobumitsu” (信光), real name Sakō Shin´ichi (佐光信一), born June 24th 1905, student of Kojima Katsumasa (小島勝正), he worked as guntō smith and died July 21st 1993, ryōkō no retsu (Akihide)
Could I get a clear shot of that stamp at the top. It's likely a Gifu stamp.