This gesture has been around for a long time in Japan, but it became known around the world thanks to social networking services including TikTok.
Index fingers touching
It can be seen in manga and anime when the character is shy and bad at talking to others.
がんばる子
You rarely see it in a real life.
Index fingers touching (or twiddling)
↓
to be shy
もじもじ
もじもじ is a word to describe a person who shows the index finger gesture with pigeon toed.