comfortably; pleasantly; cheerfully
Describes a comfortable, pleasant state or manner, often used with verbs like 過ごす, 眠る, or 笑う.
I was able to spend time comfortably on the new sofa.
She gave a cheerful laugh for me.
Expresses doing something with a willing, positive attitude, often in response to a request or invitation.
He willingly helped me.
Please accept it gladly.
快く means doing something willingly and cheerfully, the opposite of 渋々's grudging reluctance.
Derived from the adjective 快い (こころよい, 'pleasant, agreeable') in its adverbial form. The kanji 快 means 'pleasant' or 'comfortable'.