If you have coarse or curly hair, you’ll likely get irritation and razor bumps shaving this way. Hairs are pulled up while shaving against the grain and cut beneath the skin, when the blade lets go of them they will not retract to the exact same position. And consequently, they continue growing into the skin instead of out of the pore. For a closer shave, just complete more passes with the grain, relathering before each one. You might also try shaving “across the grain.”