Keira is the most difficult bachelorettes to impress and is also very difficult to reach. She is first encountered on the final level of the second mine, where she gives the player the Legendary Sword. From then on, she is found on the 255th floor of the third mine. When the player meets Keira for her heart events, she will be sleeping in her bed.
Gifts can be given to her, even though she's in bed, and there is a sign with instructions for her heart events. All of her heart events are "fetch" type events, asking the player to give her a specific gift. The floor that Keira sleeps on will be empty, the soil already tilled, except for the bed and the sign.
Keira cannot speak due to a curse put on her by the Witch Princess. She will never speak, even if you marry her. She will communicate by writing on a board.
If the player is already married, the sign in Keira's room will say that she's happy.
Note: Although all the events ask you to bring her something, it is not the same as giving her a gift that she likes, meaning you can do the event, and still bring her something to raise her affection for you.
Every heart event is basically dropping down to the 255th floor, reading the sign, and bringing her something she wants that is hinted by the sign. If you read the following information, you can skip the extra trip by bringing what she wants the first time you drop down.
Black Heart Event
This will trigger the first time you visit the 255th floor of the third mine. You will find the sleeping princess in her bed in the middle of the floor, and a sign by her bed. The sign will request that you bring her a curry dish (Ultimate or Finest Curry only).
Leave and come back, and once you leave that dish by the sign, you will finish the event.
Purple Heart Event
Once again, drop down to the 255th floor of the third mine, after you have seen the previous event.
The sign will say "I'm thirsty" this time, and you will need to bring her a Relax Tea.
Blue Heart Event
Once again, drop down to the 255th floor of the third mine, after you have seen the previous event. The sign will read "I want precious stones now. Well. Bring me [a/an] _____", the blank being a random stone.
This time, you will have to make two trips, since the stone she requests will vary for each game.
Yellow Heart Event
Once again, drop down to the 255th floor of the third mine, after you have seen the previous event. The sign will say "I love Gold Lumber. Bring them".
Do as the sign says, and you will have completed the final heart event.