Plaza Rental management guarantee Co. Ltd. Reimbursement agreement

Hello, sorry if this is the wrong place to post this. My friend put themselves down as the guarantor of a person they are no longer in contact with and my friend just got a letter in the mail from Plaza Rental management Guarantee Co.Ltd. about having to pay 24,000 yen to them after apparently this person who they are no contact with left an unpaid bill. Is there any suggestions on what can be done here? Is this legitimate? The letter says the due date is by the 31st of October. Any advice would be greatly appreciated and thanks for taking the time to read this.

by Wordsmithwit