That's why you don't let your girlfriend touch your phone. Too many dark secrets saved in your SD folders

There's also the "oh shit, I'm late for work" option, but you're option's much more fun.

Considering the entire trashcan full of used condoms and tissues, it may just be "oh shit, it's already TUESDAY?!"

Bunny-senpai said:
That's why you don't let your girlfriend touch your phone. Too many dark secrets saved in your SD folders

My interpretation is that the phone is full of drunk photos of her from the night before.

「え！？もう６日！？」
"Eh!? Already the 6th!?"
(or maybe, but unlikely:)
"Eh!? Already 6 days!?"

speck said:
「え！？もう６日！？」
"Eh!? Already the 6th!?"
(or maybe, but unlikely:)
"Eh!? Already 6 days!?"

Considering this was uploaded January 6th, it's probably the former.
6 days would more than likely be 6日間.

speck said:
「え！？もう６日！？」
"Eh!? Already the 6th!?"

Pixiv title: あけましておめで・・・ (Happy Ne...)

speck said:
「え！？もう６日！？」
"Eh!? Already the 6th!?"
(or maybe, but unlikely:)
"Eh!? Already 6 days!?"

's a Hell of a New Year's celebration.

I'm reminded of Kyon saying something like how he'd screw Mikuru ten times a day if she was his girlfriend...

NWSiaCB said:
I'm reminded of Kyon saying something like how he'd screw Mikuru ten times a day if she was his girlfriend...

Somehow I think you've greatly paraphrased whatever it is you're remembering him saying.