≠ (≠ ノットイコール, lit. "Not Equal") is a manga series by Reibun Ike. It was serialized in Be x Boy GOLD.
After meeting with his father who has been apart from him ever since he was an infant, Ryou suddenly time traveled to 22 years ago! He was sent to the late Shouwa period. After that, there's also his father, Konomi, who is just three years below him...! With the unfamiliar environment and the anxiety from the inability to go back to the past just heightens Ryou's worries. While trying to recover his transparent-like existence, his feelings began to change... A story released by Reimon, a long genuine series, first volume!