carefree, indifferent manner
恝 centers on a detached, untroubled state of mind: being carefree or showing an indifferent manner, as if emotionally uninvested.
恝 combines 㓞 (a component associated with cutting or engraving) with 心 (heart/mind). The exact historical development is uncertain, but the combination likely suggests a mind that is cut off or detached, fitting the carefree/indifferent meaning.
The top 㓞 looks like a tool cutting, and the bottom 心 is the heart. Imagine cutting away your worries so your heart becomes carefree and indifferent.
For カイ, picture a carefree person flying a kite: kite -> カイ, and the kite drifts indifferently in the sky while the person's heart is untroubled.
—