【七式重爆「富嶽」乙装備型】　夜間の長距離爆撃任務の際、護衛戦闘機が十分な数だけ追随出来ない為考案された編隊防御用の富嶽の改良版。胴体下面に配置された4連装96門の20mm機関砲の他、従来型の富嶽の装甲と武装の強化した機体である。特に編隊内に毎回ランダムに配置される為、機体下面の死角から攻撃する戦法が取れず独逸夜間戦闘機隊にとって頭痛の種だった。特に藤原中尉の居る部隊（指揮官は上白沢 慧音少佐）の敵夜戦撃墜率は凄まじく、その化け物染みた火力から機体下面への攻撃は「正直者の死」と呼ばれ独夜戦部隊からは恐れられ、駐留先の英国では富士山の噴火になぞらえて「フジヤマヴォルケイノ」と皮肉られる始末である。

【Type 7 heavy bomber Nakajima G10N-2 "Fugaku" - Type-B armament】　
A remodeled G10N-type gunship used in defensive bombing formations. It was designed because a sufficient number of escort fighters weren't able to provide escort during long-range night bombing missions.
The underside of the fuselage is equipped with 4 20m cannons (for a total of 96). It is more heavily armed and armored than the conventional G10N. The biggest pain in the neck for the Luftwaffe night fighter pilots was especially that the gunship was always positioned in a random location in the bomber formation. The reason for this was so that the enemy couldn't employ the tactic of attacking the bomber's blind spot under the fuselage with the "Schräge-Musik":http://en.wikipedia.org/wiki/Schräge_Musik .
The unit containing Sublieutenant Fujiwara (commanded by Lieutenant Commander Kamishirasawa Keine) had such an impressive kill rate with the supernaturally strong firepower. So, Luftwaffe night fighters were afraid to attack the bomber formation from below, and named their former tactic "'Honest Man's Death.'":http://en.touhouwiki.net/wiki/Imperishable_Night%3A_Extra_Spell_Cards#Spell_Card_199 However, in the British Isles where the crew were stationed, RAF members sarcastically began to call the aircraft "'Fujiyama Volcano'":http://en.touhouwiki.net/wiki/Imperishable_Night%3A_Extra_Spell_Cards#Spell_Card_202 , after the eruption of "Mt. Fuji.":http://en.wikipedia.org/wiki/Mount_Fuji
The name "Fugaku" originated from the dormant volcano Mt. Fuji.