^Weird would be an accurate translation
Karin was insisting that her stomach had a heartbeat and getting Tomoko to feel it to confirm, but Tomoko kept saying she couldn't feel anything.
If I had to guess on what was going on
Explanation 1. Karin making excuses for gas
Explanation 2. The thinnest excuse possible to get close to KanaTomo
Explanation 3. Someone get this girl to a hospital
I'd go with #2, but either way, Karin is a goober and we love her.