taru-adjective, adverb taking the 'to' particle
Literary 'taru' adjective describing a joyful or cheerful manner. Often used adverbially with と (欣然と) to mean 'gladly' or 'with delight'. Rare in modern conversation; mainly found in written or formal contexts.
He gladly accepted upon hearing the news.
The old man cheerfully gave directions to the young person.
Standard kanji form for this literary adjective.
Rare variant kanji form; 忻 is an uncommon character.
The kanji 欣 means 'rejoice' or 'take pleasure in', and 然 is a suffix forming adjectives/adverbs describing a state. The reading きんぜん is the on'yomi. The variant 忻然 uses a rare character 忻 with a similar meaning.