If you see someone you don't know as your recommended friend in Kakaotalk,

pu1. When a friend is added to Kakao Talk, it is when the other person registers his or her phone number

2017-11-18

OK

pu2. When you register your phone number, you automatically add a friend to Kakao Talk, and in that case, it appears as a recommended friend

2017-11-18

OK

pu3. If it is a friend who advertises, it appears as a recommended friend or if you register your phone number and add it to Kakao Talk

2017-11-18

OK

pu4. There are times when people who don't know anything are added, but it's probably like someone else has an old number

2017-11-18

OK