Ok forgive me. I dont know your waifu's personality or what they're from so, being general.

Prompt: Anon tossing snowballs at Mari's window, not knowing the window is open and has no screen.
Mari was sitting at a desk in her bedroom. It snowed yesterday, but there was a pleasantly cool breeze flowing in through the window.
Suddenly she received a text from anon, "Are you home?"
M- "yes, why?"
A- "Just wonderin. What are you up to?"
M- "Just doing stuff in my room. What are you up to Anon?"
A- "Wait and you'll see"
Mari sat confused. But she trusted Anon so she decided to wait. Expecting to wait for him to send her a picture.
She heard a thud from the side of her house. What she didn't know is Anon missed the first throw.
She walked towards her window to investigate.
BAM. A snowball nails her in the face. It splatters apart and snowflakes fall all around her.
After the initial surprise, she leans out window and spots Anon. Who is shocked and has his hands over his mouth.
M- "ANON. WHAT THE HELL?"
A- "I didn't know your window was open!"
M- "You couldn't see the visibly open window!?"
A- "No! And why dont you have a screen?"
M- "Because of all the times we sneak in or out of my room!"
A- "Okay well, I'm sorry."
M- "It's gonna take more than that Anon, I have to clean my room now."
A- "What will it take?"
M- *angrily deciding* "Take me out to dinner tonight! At a nice place."
A- "Of course yeah!"
The 2 discuss where to go and when to do it. Once things settle down, Mari invites Anon inside and they both clean the snow off her bedroom floor.
M- "We're still doing dinner."
A- "I wouldn't ever pass up a chance to go out with you."