noun, na-adjective, adverb
deeply moved; even more emotional
A somewhat literary set phrase meaning one's emotion is heightened or felt more deeply than before, often used in reflective or narrative contexts.
久しぶりに故郷を訪れ、感慨一入だった。
Visiting my hometown after a long time, I was deeply moved.
彼のスピーチを聞いて、感慨一入の思いがした。
Listening to his speech, I felt even more emotional.
感慨無量 means 'deep emotion' or 'profound feeling', while 感慨一入 emphasizes that the emotion is felt even more deeply than before or than expected.
The phrase combines 感慨 (deep emotion) with 一入 (ひとしお, 'one more layer' or 'even more'), literally 'emotion one layer deeper'. The exact historical derivation is uncertain, but it is a fixed literary expression.