訓 なか ・ 音 チュウ
Sino-Vietnamese: trung
A vertical stroke skewering a box exactly through its centre, like an arrow hitting the bullseye. Dead middle, and therefore inside.
Stroke data: KanjiVG (CC BY-SA 3.0) — kanjivg.tagaini.net
かばんの中にペンがあります。 (かばんのなかにぺんがあります)
There is a pen inside the bag.