Dr. Daisuke Serizawa was a scientist who first appeared in the 1954 film, Godzilla.
Serizawa was a young colleague of paleontologist Kyohei Yamane, and also fought in combat during WWII, where he lost his right eye in battle.
After the war, Dr. Serizawa became a scientist, who studied elements and their effects on other objects and organisms, and eventually discovering a new element that could create a destructive chemical reaction that liquefied molecules by separating their oxygen atoms known as "micro-oxygen". Initially, he was horrified by the destructive potential of his "Oxygen Destroyer". However, he chose to continue researching it, confident that he could take it beyond its raw form and develop it to benefit society. Meanwhile he kept its existence secret from everyone.
Shortly after the first sightings of Godzilla, Dr. Serizawa decided to reveal his secret experiments to Kyohei's daughter Emiko when she visited his home. After shocking her with the horrific effects of the Oxygen Destroyer, he swore her to secrecy, explaining that he knew that the world was not ready to know of such a terrible weapon. He remained in his lab during Godzilla's attacks on Tokyo, continuing his research.
Emiko soon returned to Serizawa's lab with Hideo Ogata in tow, hoping to convince him to use the Oxygen Destroyer against Godzilla. Serizawa adamantly refused, explaining that his weapon would only begin a new age of terror once the world saw what it could do. He briefly scuffled with Ogata in defense of his decision, but eventually paused when he saw a report about the destruction Godzilla had brought upon Tokyo. Shaken by the utter destruction, Serizawa finally agreed to use his device, but warned Ogata that he would only use it once. Afterwards, he burned all of his micro-oxygen research papers.
When Serizawa and Ogota found Godzilla on the seabed, Serizawa activated the device and watched Ogata return to the surface before cutting his own line and dying with the monster. With the only copy of the Oxygen Destroyer used up, his notes destroyed, and his own life at an end, Dr. Serizawa hoped to ensure that no one would ever discover the same terrible power he had just unleashed.