1. There is a written agreement that the mobile phone is only for the man to use and is not a gift.

2. There is a written agreement that the mobile phone is given to the man, but if there is an accident (cheating, accidental death, etc.), the man must return it to the woman.

3. There is a written agreement stipulating that the man borrows the money to buy the mobile phone from the woman.

4. The man has a suicide note and agrees that the mobile phone will belong to the woman after his death.

In addition, legally it should be regarded as a gift, and the ownership belongs to the man. When the man dies, it will be treated as his inheritance according to the legal inheritance.