Here are the voltage and current shown for the primary winding of a transformer or an ideal inductor when the voltage is sinusodial.

My question is why the current is increasing when the voltage is decreasing as shown in the black box ? Its obvious that current should be increasing with increasing voltage and current should be decreasing with decreasing voltage but here the current is increasing for decreasing voltage. 

And the current decreases during the negative voltage cycles only. 

What is the the reason behind all this ?

[![enter image description here](https://i.stack.imgur.com/1hEBc.jpg)](https://i.stack.imgur.com/1hEBc.jpg)