One Heart contains the following:
- Many, many references to death (one of the leads is dead, after all)
- Murder
- Grief
- Trauma
- Depiction of almost drowning
- Detailed horror imagery (ghosts, blood, bones, body parts where they shouldn't be, etc.)
- Estranged family
- Unintentional misgendering
- Cannabis and alcohol use
- References to drugs and addiction
- Presence of a fascist political party
- Explicit sexual content in chapters 23, 25, and 32
- References to deceased parents
- References to deceased pets (but they're actually fine! trust me)