concerned about
忓 centers on a state of anxious preoccupation: being concerned about something or someone, with a nuance of mental unease.
忓 combines the heart radical 忄 with 干, which likely contributes a phonetic element. The exact historical development is uncertain, but the heart component suggests an emotional or mental state.
The heart radical 忄 beside 干 (which can mean 'shield' or 'intervene') suggests a heart that is constantly on guard, worrying and being concerned about potential threats.
For カン, imagine a concerned person holding a can of worry beads: can -> カン, and their heart is full of concern.