The missing detail is your time horizon. If this is preparation for a purchase soon, mortgage comparisons and a jurisdiction-specific legal checklist deserve attention alongside price data. If it is longer-term research, build a small set of comparable detached homes and record location, age...
Completed August transactions may reflect negotiations that began before August, depending on the deal timeline. That makes the source date important: listing activity, agreed deals and recorded completions should be kept in separate columns rather than treated as one August snapshot.
I would not treat the whole ¥3,213,000 as available for the flat. First ring-fence your general emergency fund, then set aside every known payment due before your next reliable income: moving, service charges, insurance and the mortgage payment. What remains is the repair and furniture budget...