if you do a favor for someone, you will get a return favor; if a fish is friendly toward water, water will be kind to the fish too; you scratch my back and I'll scratch yoursproverbsee also 魚心あれば水心
if you do a favor for someone, you will get a return favor; if a fish is friendly toward water, water will be kind to the fish too; you scratch my back and I'll scratch yoursproverbsee also 魚心あれば水心