Given the size of this ship, the size of its main battery (460 mm or 18.1 in), and my dim recollection of IJN warship names in kanji, I would hazard a guess this is supposed to Yamato's sister-ship Musashi (武蔵) modernized in much the same way the Iowa-class battleships were IRL.
No idea how they managed to put an extra 6 knots into her top speed (33.5 knots up from 27.5).
Given the size of this ship, the size of its main battery (460 mm or 18.1 in), and my dim recollection of IJN warship names in kanji, I would hazard a guess this is supposed to Yamato's sister-ship Musashi (武蔵) modernized in much the same way the Iowa-class battleships were IRL.
Or rather, in a manner similar to the much more extensive modernization that was considered for the Iowas, complete with AEGIS and VLS launchers, but was ultimately rejected as too impractical.