|Rōmaji||Kiken na Shimai|
|Air Date||February 19, 2016|
|Opening||GATE II ~Beyond the World~|
|Previous Episode||The Magic City of Rondel|
Dangerous Sisters (危険な姉妹 Kiken na Shimai) is episode 19 of the Gate - Thus the JSDF Fought There! anime.
With the Emperor bedridden, Zorzal takes over the throne and declares his intent to avenge the Empire's humiliation from the Japanese. With the Imperial Capital in curfew, the JSDF forces in Akusho are trapped and the Japanese Ambassadors put under house arrest.
To Pina's anger, not only has Zorzal arrested the pro-peace faction on charges of accepting bribes from Japan, promoting his loyal followers and planning to attack the Japanese again with unconventional and unethical tactics, but her other brother Diabo has run away to seek help from other kingdoms to overthrow Zorzal even it mean the end of the Empire.
Meanwhile in Rondel, Arpeggio's master Mimoza offers her student's help to Itami in his mission as she is an expert of minerals. Mimoza also reveals something interesting to Itami and the others about the Gate: Every few centuries or millenniums, the Gods of the Special Region would open a portal (the Gate) to another world at Alnus where the races of those worlds would come and settle in Special Region, explaining why they are many different types of races living here.
When Arpeggio angrily learns Lelei has made Itami her husband due to their tribe tradition where couples who sleep three nights consecutively together are considered married, the sisters have a magic duel to settle their dispute. However, an assassin tries to kill Lelei at the end of the match but is saved by Grey. Grey and another Rose Knight, Shandy, reveals to Itami and his group that the assassin was sent by Zorzal due to his jealousy of Lelei's fame of defeating the Flame Dragon and the two of them came to protect them under Pina's orders. Rather than stay and fight, Itami decides it's best they run away instead.
- In the anime, Arpeggio only carries her magical beads during her duel with Lelei while in the manga, she is shown to carry additional magical staff in her left hand.
- Grey kills the assassin with a claymore in the anime while he kills the assassin with a knife in the manga.
- Apreggio doesn't use her special move: Big Sister's Authority in the manga.
- In the anime, only one mage uses defend spell against Apreggio's stray magic blasts while in the manga multiple mages are seen using the defend spell.
- Lelei doesn't use ice summoning spell in the anime.
- Lelei doesn't use her fly spell in the manga.
- In the anime, Lelei shows her sister and Mimoza her laptop while the in the manga, she shows them her book with modern printing technique from Japan.
- Rory doesn't show her jealousy about the ceremony of three night in the manga.