He is a college student at Futo University who fell in love with Himeka Yukimura when she called him her "prince". However, he soon realizes that Himeka tells this to any male who assists her, plaguing him with the thought that she will never love him back and giving him insomnia as a result.
He acquires the means to become the Nightmare Dopant in order to inflict this same pain on Himeka, by making sure she does not get a good night's sleep in fear of his attacks. In his Dopant form, Fukushima uses his dream manipulation powers to trap all of his rivals for Himeka's affections in their worst nightmares before using a massive dreamcatcher-like net to place them in a coma.
Each victim is branded with a letter H on their foreheads, standing for both "Himeka" and "Hajime". Though he fakes being among the victims to get Shotaro Hidari off of his trail, Fukushima is found out and his Nightmare Memory is destroyed by Kamen Rider Double Luna Metal's Metal Illusion Maximum Drive.