Wrinkle-chan
The nickname given to a girlfriend that is much older than you. Wrinkle as in old but still cute.
"My wrinkle-chan might be much much older than me, but she is so much more mature and knows what she wants in life."
"Are you visiting your wrinkle-chan again?
-yes, we're planning on reading poems under the moonlight."
"Are you visiting your wrinkle-chan again?
-yes, we're planning on reading poems under the moonlight."