Iijima is best known to most fans as the writer and director of Ultra Q, the first entry of the Ultraman franchise. He also worked on the original Ultraman series, most notably his work in the first two episodes, with the second episode being notable for the introduction of Alien Baltan. Baltan later became a popular antagonist in the franchise. Iijima also worked on Ultraseven, Return of Ultraman, and other entries in the franchise and often times he worked under a pen name.
He later retired in 1992, but he continued on working. His last notable works in the Ultraman franchise was Ultraman Cosmos: The First Contact film, and Ultraman Max episodes 33 and 34, which features another notable appearance of the Alien Baltan. He both wrote and directed said projects. From all of us here, thank you for the memories.
[Source: Anime News Network, Tsuburaya; additional info: Wikipedia]