Rainy Brother 1 appears in B1F and B2F of the Secret Laboratory within the Midnight Channel on rainy days. After being defeated, it may drop 1st Boy's Talc. Selling the 1st Boys Talc will unlock the Bloody Kunai weapon for Yosuke Hanamura in the shop, which has the second highest attack rating of weapons available from the Secret Laboratory but boost the damage of his Wind spells by 25%.
In Golden, it appears in B1, B2, B5 and B6. It may drop Meteorite, Rose Quartz or Buffalo Stone.