I know, this manhwa translates the novel well but of course there are discrepancies and this is one of them that got lost. Also, his "safe" is not just under the sofa but a hole under the sofa so the money can't be seen but some is letting him hide them.
**SPOILERS**
After some time (more than a month) he could barely fit in the hole because his puppy tummy got fat (so cute)
I started fr the beginning since the manga just started, plus I wanted to see the difference between the two media. It's a fast read and translation is decent.
Here's the link. Btw, I just got this fr another fan here in the comments so thank her:
https://blossomtranslation.com/story/dont-mess-with-the-puppy/
Spoiler(?)
I'm reading the novel right now and I'm sad that they changed some things going from novel to manhwa. For example when MC kept stashing money under the couch and the big bundle fell in front of him, he looked up and ML had his hand up because he dropped it on purpose and was smiling at him. I just thought the situation was funnier with the novel setting