Kagawa admits he discussed the No7 shirt with officials during his whistlestop medical.
"We did [discuss it] but nothing will be confirmed until Sir Alex comes back," Kagawa explained. "Since I am very new to the club, I have no intention to get an important number. Let's wait and see how it goes.
"I just told them my hope because I didn't know which numbers are available.
"Having completed the transfer, I can't think anything negative anymore. I feel positive. I would like to achieve big things with such a big, historical club. I know there's a tough challenge ahead of me but I am excited to have the chance to take it."