2020’s Tuyo is the first volume of Rachel Neumeier’s seven-book (so far) Tuyo secondary-world fantasy series.
Warleader Garoya of one of the Ugaro clans had thought it would be easy to raid the Lau; it wasn’t. The raiders must retreat. Garoya leaves his younger brother Ryo behind, as a tuyo. A tuyo is a prisoner handed over the enemy as a sacrifice.
Ryo is tied to a stake and left for the Lau.