Please can anyone tell me what is the purpose of the greyed out button on the menu after you click 'Play with Pikachu'? The first button is to engage in play with the partner, the second button.... nada. I can't find the answer anywhere. It's like I'm the only one wondering about it.
As shown circled below, the second option in the partner play menu is for Secret Techniques. Secret Techniques are the HM equivalents from the main series games, allowing you cut down trees, move boulders, etc..
It will be grayed out until you learn your first secret technique. If I remember correctly, this is during the events on the S.S. Anne, and speaking to the captain.