Тука Луна Марсо

This beautiful elf girl is the only survivor from her village, which was destroyed by the dragon. She was very dedicated to her father, who died protecting her. Saved by Japanese soldiers, Tuka Luna lives among the refugees in their military camp.

Unable to cope with the loss of her father, she first acts as though he is staying at the base, insisting on two rooms and extra portions of meals. Her mental stability deteriorates over time and eventually, she latches onto Itami, calling him "father." In an effort to bring her to her senses, Itami brings Tuka along on the hunt for the Flame Dragon and forces her to aid in its defeat. Having avenged her father, she recovers — but refuses to stop calling Itami "father," claiming it had become a habit.

(Source: Gate - Thus the JSDF Fought There! Wiki)