、。
Two male students sharing an umbrella — now that's quite the scene.
Literal
Male-students mutually [possessive-の] shared-umbrella [question-か], quite tasteful situation [copula-だな].
男子学生同士 ('male students together') uses 同士 ('together, mutually'). 相合傘 (あいあいがさ, 'sharing an umbrella') is a romantically coded image in Japanese culture — two people walking under one umbrella suggests intimacy. なかなかオツな ('quite tasteful/chic') uses おつ (乙) for unexpected charm. The speaker is amused by the homoerotic undertones of the scene.