一往情深

yīwǎngqíngshēn
  1. deeply attached
  2. devoted

CEDICT

to have a deep and abiding affection for; to be passionately devoted (to something, once one starts to pour one's feelings to it); to be passionately in love

Wiktionary

语本南朝宋．刘义庆《世说新语．任诞》：「桓子野每闻清歌，辄唤：『奈何！』谢公闻之曰：『子野可谓一往有深情。』」指人情感深厚、真挚，一旦投入，始终不改。

重編國語辭典

对人或事物具有深厚的感情

維基詞典

Entry Composition

1 一 yī
  1. one
  2. single
  3. a (article)
  4. as soon as
  5. entire; whole; all; throughout
  6. "one" radical in Chinese characters (Kangxi radical 1)
  7. also pr. yāo for greater clarity when spelling out numbers digit by digit
=2 往 wǎng
  1. to go (in a direction)
  2. to
  3. towards
  4. (of a train) bound for
  5. past
  6. previous
=2 往 wǎng old variant of 往 wǎng
3 情 qíng
  1. (bound form) feelings; emotion; sentiment; passion
  2. (bound form) situation; condition
=4 深 shēn old variant of 深 shēn
=4 深 shēn deep (lit. and fig.)

Related entries

忠诚 zhōngchéng
  1. devoted
  2. loyal
  3. fidelity
  4. loyalty
翻译就像一个女人。她漂亮就会不忠诚；她忠诚就肯定不会漂亮。

Translation is like a woman. If it is beautiful, it is not faithful. If it is faithful, it is most certainly not beautiful.

Source: Tatoeba

耿耿 gěnggěng
  1. bright
  2. devoted
  3. having sth on one's mind
  4. troubled
谆谆 zhūnzhūn
  1. earnest
  2. devoted
  3. tireless
  4. sincere
  5. assiduous