那年我们都很天真
[nèi nián wŏ men dōu hĕn tiān zhēn]
'Back Then, We Were So Innocent' refers to a reflective sentiment about the naivete and sincerity of youth, looking back on past experiences or periods. This term can imply nostalgia for simpler times without ulterior motives or worldly knowledge and it carries some regrets or cherishing emotions for lost innocence.