Body
The sound /ch'/ is aspirated (pronounced with a breath or puff of air)—like the sound /ch/ as in church in English.
/ch/
VS.
/ch'/
chwi, ch’wi
ch'wi-mi
chae, ch’ae
ch'aek-ssang
chi, ch’i
ch'il-p'an
chǒ, ch’ǒ
si-ch'ǒng
ch'ǒn-ma-ne-yo

Yǒng-mi:
Ma-i-k’ǔl-ssi-nǔn
ch’wi-mi-ga mwǒ-ye-yo?
Michael:
chǒ-nǔn tǔng-sa-nǔl cho-a-hae-yo.
Yǒng-mi-ssi-nǔn ch’wi-mi-ga
mwǒ-ye-yo?