Me:just want to belong to you very briefly.

不是吧。
我觉得应该是：
我：只是想短暂的和你呆在一起。
就是短期属于你之类的。
给个定义作参考吧,剑桥的。
是说briefly意思是一小段时间
adverb
We chatted briefly (= for a short time) about the weather。
Briefly (= Using few words),the company needs to cut its expenditure。