Contracting いる+の to いんの
The verb いる followed by the particle の may contract as いんの.
Examples
名探偵コナン » Volume 9 » Page 11
orange » Volume 5 » Page 30
ひとりぼっちの○○生活 » Volume 1 » Page 107
The verb いる followed by the particle の may contract as いんの.