Banks, whose business performance is principally determined domestically, proved immune to today's reversal. Mizuho, the world's largest lender by assets, gained 6,000 yen, or 2.4%, to 254,000, Sumitomo Mitsui picked up 2,000 yen, or 0.4%, to 505,000 and UFJ firmed 13,000 to 295,000, up 2.7% .