¥4,590,000 sounds substantial in isolation, but the purchase price is also substantial, so I wouldn’t judge the buffer by its headline amount. Work backwards from the cash you refuse to spend: living emergency fund, known completion and moving payments, first mortgage payment, insurance excess...
Run three versions of the monthly cost: today’s association and insurance figures, a further increase, and no reduction at all over your intended holding period. Then add likely vacancy and management workload if renting it out is a fallback plan. If the apartment only beats rent when fees...