Sakurako-san is a weird one, preferring bones to people and all, but she’s full of wisdom and thinks and looks like no one else around her. Yet she also has her own brand of empathy, seeing even emotions like happiness, relief, and comfort as brain chemistry reacting to external stimuli.
She’s also quite human and thus fallible herself, which is what makes her so endearing as a character. She persists in calling Shoutarou “boy” (shounen) as a way to distance herself from him, despite their growing bond that, at times, treads into romantic territory.
Sakurako persuades her self-professed “guardian” to accompany her through some caves, then to a park where they’re pointed in the direction of human remains by a far more normal couple. Saku’s delighted at the find, and gives a beautiful description of how a corpse out in the open is briefly a “paradise of life” as flies lay eggs, maggots feed, and predators feed on the maggots, etc. She has a deep appreciation for the circle of life and the food chain, things humans don’t need to think about in daily life.
When Shoutarou does the responsible thing and phones the police, it doesn’t stop Sakurako from offering her expert opinion on who the corpse was and what happened. The police, however, aren’t so much impressed by her expertise as annoyed by her interference and what they perceive as arrogance (and hey, she is a bit arrogant).
Back home, when Shou thinks Saku is sulking, she’s actually concentrating on building a skeleton. That’s when she finally tells him what he’s been meaning to ask about: her dead little brother, Soutarou, just one syllable removed from his name. It’s not much, but it’s the start of a dialogue and a sign she’s willing to gradually let Shou in.
The next day, Shou goes to a cafe at the request of his classmate Kougami Yuriko. Her purpose is to thank him for helping to find the corpse, which was that of her grandmother, who the police believe jumped to her death. When she invites both Shou and Saku to her house to thank them properly, we learn her grandma was taking care of her husband, who was suffering from severe dementia and required round-the-clock care.
That burden is something the police used as a motive for Yuriko’s grandma’s suicide, and Yuriko even understands and doesn’t hold it against her. On the contrary, she’s ashamed she and the rest of her family didn’t see how tough it was for her until it was too late. But when she asks Saku to show her where and how her grandmother died, she gets an entirely different and more plausible story than the police came up with.
When they return to the site where her grandmother’s remains were found, Sakurako presents that story, which is this: her grandmother didn’t go there to die, she went there to live. She just stumbled and fell off the cliff in an unfortunate accident.
The reason she left in the middle of the night was so that she could reach a certain spot so she could see the same sunrise her husband painted back when he was healthier. Sakurako points out how exposure to the morning sun releases serotonin, which calms and soothes the mind. She tempers her conclusions as mere speculation, but they fit the facts, the timing, the motive, and the details.
These conclusions also provide comfort and closure to Yuriko. Now that she knows her grandmother didn’t give up on her grandfather, she has that much more reason to be strong and provide care in her granny’s place. Another satisfying mystery that respectfully delved into a specific (yet under-represented in anime) circumstance in modern human society—caring for those who can’t care for themselves—and built logically to a life-affirming finish.