delighted, pleased
昪 centers on a bright, cheerful emotional state: feeling delighted or pleased, as if lit up by the sun.
昪 combines 日 (sun) with 弁, which likely contributes the sound. The idea of sunlight may connect to brightness and delight, but the exact historical development is uncertain.
The sun 日 shines over 弁, like a bright day that makes you feel delighted and pleased.
For ヘン, imagine a hen basking in the sun, looking delighted: hen -> ヘン, and the happy hen captures the pleased feeling.