最后一个夏天我们要说再见
[zuì hòu yī gè xià tiān wŏ men yào shuō zài jiàn]
It means 'We will say goodbye in the last summer.' This expresses parting at the end of a beautiful, shared period with lingering reluctance. It suggests that the person probably has some bittersweet reminiscence about endings or farewells.