The He-111 was designed by Siegfried and Walter Gunter in 1934. The project described as a Wolf in Sheep's Clothing because the project was disguised as a civilians transport to by pass the Treaty of Versailles. It was designed to give the Luftwaffe a fast medium bomber with a decent range. The He-111 can be recognized by its distinctive glazed greenhouse nose of the H variant. The bomber proved it self well until the Battle of Britain where it's defensive armament was not able to take down RAF aircraft.
Nevertheless the He-111 was a rugged aircraft and proved hard to shoot down and many remained airborne. It remained in service for the entirety of the war and could be found on almost any front.
In the Anime
Presumably the He-111 saw combat in Livonia and Thermidor and was essential part of the Germanian Air force's bomber fleet. It was used in the Invasion of Eylstadt during the opening assault, the Battle of Coenenburg and the Fall of Eylstadt.