Laplace's Witch (2018)

In 2018, two people in different parts of Japan die during a visit to hot springs from hydrogen sulfide poisoning. Not sure whether this is a murder or an accident, the police are involved in the investigation of the famous biochemist Syusuke Aoe. During the investigation, the professor encounters a high school student Madoka, who tells and proves to him what happened and why. Meanwhile, a third person dies of poisoning.