Born in Helsinki, the capital city of Suomus, she entered a training school at the same time as her witch abilities emerged and was trained as a Non-commissioned Officer. At this time, her careless attitude has already appeared, and the training unit has been completely destroyed many times.
After graduation, she was appointed Flight Sergeant and assigned to the 3rd Company of the 24th Squadron, an elite unit of the Suomus Air Force. As Eila Ilmatar Juutilainen is also a member of this squadron, the two are fellow squadron members. Although she shot down a Neuroi on her first sortie, she was hit and the engine got damaged, and crashed while returning to the base. One of the causes is her strong fighting spirit and her fighting style being continuous attacks with no regard for shields.
Going by the numbers, she is an excellent ace, but due to the number of times she has lost Striker Units, no matter whether it was due to being shot at, crashing in flight, encountering engine trouble, or other unforeseeable accidents, she is also called "Unlucky Katajainen" by those around her. However, she has never gotten any teammates involved in her accidents, and has never suffered any lethal wounds despite all of this. She is also called "Crasher O'Hare the Second", as both of them are infamous for Striker Units accidents.
With the number of irreplaceable strikers she destroyed, and her not showing any signs of remorse, she was pulled from front-line duty for a time, and put to work cleaning the hangar, serving coffee and other minor tasks. Since Suomus relies on imports for procurement of Striker Units and has limited supplies, it was difficult to handle witches that would destroy the equipment.
In 1943, she was invited to the 502nd Joint Fighter Wing and became known as the "Break Witches" along with Waltrud Krupinski and Kanno Naoe due to often damaging their striker units. When she was stationed at the Joroinen Observatory in winter 1944, she reunited with Eila Juutilainen for a short time and made the acquaintance of Sanya V. Litvyak.
Nikka is something of a tomboy, bearing a boyish appearance and often unladylike manner, she looks like Hanna Wind's twin sister. She was once something of a delinquent, which has since eased somewhat with the influence of her close friends such as Hanna Wind and Eila. She possesses a very exacting personality which usually splits any situation into right or wrong. While not stupid, she is relatively guileless and often distracted, making her a popular subject for Eila's pranks.
She has a strong desire to do her best to protect her home town, and works hard, but her character is too straightforward and this often makes her attitude worse. She is bright and social, but in some situations she cannot read the atmosphere of the place.
Under the 502nd, she has found a similar foil/best friend in Aleksandra I. Pokryshkin, whose fussiness and nagging (a talented mechanic, it is often Aleksandra working on Nikka's broken units) tends to keep Nikka's carelessness in check.
She possesses a special magical aptitude for hyper-regeneration, and by synergizing with her familiar's healing magic, she can heal most of her injuries nearly immediately. She cannot heal other persons.
Since the magic power is circulating in her body constantly when using her magic to fly, she survives from crashes that would normally have killed her and surprises the surroundings. This ability may be responsible for her carelessness in flight and combat.
Her Bf109 G-6 (MT-476) eventually became totally unusable due to extreme wear of the magic engine.
Her Bf109 K-4 is a unit that Lieutenant Krupinski snatched from Karlsland supplies and was declared as a loss, therefore it doesn't have a unit number.
- She is referred to as "Nipa" by her friends.
- Nikka is based on the Finnish flying ace Nils Katajainen. Like Nikka, Nils had a reputation for frequently crashing his craft, often surviving with only minor injuries. Her nickname, "Nipa", was also Nils' nickname during the war.
- Her close friendship with Hasse is most likely a reference to her real life counterpart's close friendship with Hans Wind.
- Kimi to Tsunagaru Sora, Chapter 4
- Strike witches: Chii Sanya
- Strike witches: Chii Size
- Strike Witches: Aurora no Majo
- Brave Witches: Dai 502 Butai Hasshin shimasu!
- World Witches: Contrail of Witches
- Brave Witches: 502nd Joint Fighter Wing
- Brave Witches Prequel: The Vast Land of Orussia
- Strike Witches: Kiseki no Rondo, in group cards
- Brave Witches VR: Operation Baba-Yaga - Counter attack in the snow