inner box; inner case
Refers to a box or case placed inside another container, often for protection or organization.
このお菓子の箱は、外箱と中箱に分かれている。
This sweets box is divided into an outer box and an inner box.
Compound of 中 (naka, 'inside') and 箱 (hako, 'box'). The reading なかばこ is a straightforward combination.