Railguns on Japan's future BMD ships

Could Japan's planned ballistic-missile-defense ships carry railguns?

Yes, that is increasingly plausible, and the nominal two-ship class may eventually become a pair of pairs.

Japan's railgun work is advanced enough that fitting the weapon to the planned large ballistic-missile-defence hulls is becoming plausible. The ships would offer the size and electrical margin needed for a demanding future system, though installation is not confirmed. Japan also tends to procure paired subclasses or a pair of pairs. The nominal two-ship program may expand to four as the design and weapon mature. The platform and weapon programs are converging, but the forecast remains conditional.