Jiro Tomitake is a recurring character who first appears as a freelance photographer visiting the rural village of Hinamizawa. He specializes in taking pictures of wild birds and landscapes, visiting the village several times a year, a routine he has maintained since before a major local conflict known as the Dam War. His friendly and easygoing nature has made him a familiar and well-liked figure among the villagers, including the young members of the school club.

This harmless appearance, however, is a carefully constructed cover. Tomitake is not a photographer by profession; his real name is believed to be an alias. He is an operative for a secretive organization known only as Tokyo, holding the rank of First Lieutenant. His true mission in Hinamizawa is to act as an auditor, monitoring a clandestine research project on a mysterious local affliction called Hinamizawa Syndrome, which is conducted at the village clinic. His background is in the military; he was once an expert sniper and a professional sniping instructor for the Japan Self-Defense Forces. An accident that damaged his vision led to his removal from active duty, after which he was recruited by Tokyo for his skills. His former profession as a sniper provides him with the steady hands and immense patience that also make his photography cover story plausible.

In the majority of the story's arcs, Tomitake meets a gruesome and seemingly inexplicable end. His body is always found after the annual Watanagashi festival, having clawed his own throat out. This death is the fifth in a series of similar mysterious deaths and is attributed by locals to a curse. The truth, as is later revealed, is that he is killed by his close associate, Miyo Takano. She injects him with a powerful strain of the syndrome that drives him to Level 5, the terminal stage of the disease, causing him to fatally wound himself. This tragic outcome ties directly to his most significant relationship.

Tomitake shares a complex and ambiguous bond with Miyo Takano. On the surface, they appear to be lovers or close romantic partners, frequently seen together at festivals and around town. Tomitake shows genuine care for her and supports her research, even as he is officially tasked with auditing it. He is, however, often creeped out or made uncomfortable by her fanatical obsessions. In the story's darker arcs, when Takano attempts to recruit him to support her plan to trigger a catastrophic event, he refuses to compromise his principles, an act of defiance that seals his fate. For her part, Takano's feelings are portrayed as complicated, as she can coldly order his death while internally questioning her own actions. Despite her betrayal, in the arcs where he survives, Tomitake ultimately works to save and redeem her, demonstrating a deep-seated loyalty. Beyond Takano, he has key relationships with other characters, working with detective Kuraudo Ooishi and clinic director Kyosuke Irie, who jokingly nicknames him Risa due to a mispronunciation of his rank.

Physically, Tomitake is a muscular man in his mid-to-late thirties with short, light brown hair. He is almost always seen wearing a pair of glasses due to poor vision. His typical attire in the village consists of a dark green cap, a black sleeveless shirt, green military-style trousers, and black boots, accessorized with a dog tag and a watch. He is rarely seen without his camera. His personality is calm and easygoing, though he is described as being somewhat awkward and not very good with women. He is earnest and respected, but can be slightly out of touch with social cues.

In the final arc of the original story, Tomitake is able to avoid his usual death thanks to a warning from Furude Rika, who is trapped in a time loop. He uses his survival to investigate Takano's conspiracy and uses his combat abilities, such as precision shooting to scare off a pursuing van, to help thwart her plans. In later sequel series, his fate varies even further; in some loops, he and Takano escape together, and he ultimately becomes a key figure in helping her atone, with the two of them eventually returning to Hinamizawa together. His role in the story is that of a man whose peaceful exterior masks a lethal past, and whose personal loyalties are constantly at war with his professional duties.