Wish I had a pure heart like yours.
This is a single kanji with an い on the end, meaning you know it's probably an adjective. What's the adjective form of pure? It's also pure. People like this are also usually really gracious to others. This type of pure heart would even be a gracious loser.
Oh man, the reading for this is... like... crazy. First part can be something like it's soggy (いさぎ)... then the second part is like the word 良い (good). So, you can think of a pure hearted person eating soggy cereal. He/she is so pure hearted that it doesn't matter to them how soggy it is. In fact, they seem to enjoy it! They keep saying "it's soggy, good!" over and over again while eating the terribly soggy food.