The phrase "Shinseki no ko to otomari dakara aki" (roughly translated from Japanese as "Because I'm staying over with a relative's child, it's autumn") is a specific title often associated with niche Japanese media, specifically adult-oriented manga or "H-manga" works.

Seasonal-anchor reading (literal + elliptical): The speaker states they’re staying with a relative’s child and appends “autumn” as a contextual marker — maybe the visit happens in autumn, or the mood is autumnal. The sentence feels elliptical: why does staying with the relative’s child imply autumn? The listener must infer a link (timing, tradition, mood).

• Setting: A rural, isolated shrine or an old Japanese house with amado (rain shutters). The sound of chestnuts roasting or kaki (persimmon) drying outside.
• The “Otomari” Scene: The child (Shinseki no Ko) has a fever because their divine powers are fluctuating. The protagonist must stay awake all night. There is one lantern. The child whispers about the stars they saw 500 years ago.
• The Dialogue: Do not say “I love you.” Say, “Samui ne” (It’s cold, isn’t it?). That is the confession.
• The Payoff: The morning after. The child is alive. The sun is low (autumn sun). The protagonist makes zousui (rice porridge). The phrase “Dakara Aki” is never spoken aloud—it is the caption on the final panel, written in the narrator’s trembling hand.

If you feel that ache in your chest right now—that specific blend of warmth and sadness—then you already understand. You don't need a translation. You just need a blanket, a rainy window, and the ghost of a sleeping god beside you.