Japan is high density as any part of the world's mega population. It stands reason an airline who has courted Boeing for so many years would dabble with the A380 as a stop gap-loosening for its high density routes within ANA's reach.
The purported pending order is for three giant A380s. Airport congestion is in play for ANA. One A380 airport slot can eliminate having several airport slots for moving traffic. However, where will the A380's land. The US, Europe and Southeast Asia are the obvious destinations. The 747 is fading and the A380 is the newest design sinking over the 747-8i. The Boeing 747 aircraft just doesn't move enough people in and out of Haneda using only one airport slot. The 777-9X isn't ready nor does it have an immediate production slot for ANA's purchasing timing for having a quantity people mover other than heir apparent A380.
Not saying that A380 is a superior aircraft over the Boeing suite of aircraft, but it is an option for meeting current needs and growth plans for ANA. Ordering three A380's solves several issues in a one type buy where current Boeing types could cover those ANA issues. As mentioned at the top, ANA needs a congestion buster even as the A380 is also a congestion maker on the ground. ANA is keeping an airport slot while moving 550 passengers in and out using its current available Haneda positions makes some sense. Even though the A380 will congest the airport landing 550 people at one gate, where it then becomes an airport problem not a ANA problem.
Grasping at straws is a strategy. The Airbus A380 ANA grasp goes only so far in a fleet family. I would be concerned for Boeing if they ordered as many as Qantas did before they discovered another way, and started buying 787-9's as part of its flexible move in the market. The operational inflexibility of the A380 is a stop gap measure for relieving only one part of ANA's airline's problems when moving passengers.