The Deeprealm Mountain is an elevated area located in a Deeprealm in Fire emblem Fates.
If Takumi is married, he will have a son named Kiragi. Kiragi is placed in a Deeprealm containing this mountain. Growing up, Kiragi would often venture into this Mountain, lined with a thick forest, in order to hunt wild game with a bow.
During a Paralogue, Kiragi is once again hunting in the mountain. Spotting a wild bear, he attempts to kill it only for his arrow to miss and hit an invisible soldier. As luck would have it, Takumi and Sakura had just so happened to be paying a visit. Seeing his son in peril, Takumi rallies the army to rescue his son. If Takumi talks to Kiragi, he will ask him if he was worried this whole time when he was trying to catch up to him. Kiragi assures him that he was not worried at all and knew that Takumi would come to his rescue. As thanks, he shows his father a bear he had just killed prior to the attack. Impressed, Takumi tells him to put their chat on hold until the invisible invaders have been dispatched.
After successfully routing the invaders, Kiragi is amazed by his father's skill and asks him to join the army so he can learn further. Takumi accepts and Kiragi leaves his Deeprealm, bringing the bear he had killed for the army to enjoy.