Level. 15 A Fleeting New Game Plus

'Level. 15 ' (強くて儚きニューゲーム, Tsuyokute hakanaki nyūgēmu) is the continuation of Level. 14++.

It's the fifteenth volume of Hai to Gensō no Grimgar light novel series despite being the seventeenth published book.

Synopsis
'When they awaken in darkness, Haruhiro and the others have lost their memories, with the exception of Merry. They must escape the destroyed Alterna to meet the forces of the Kingdom of Arabakia, set to take back the city.'

""Honestly, none of this makes sense...""

When they come to, Haruhiro and the others find themselves in the darkness. None of them remember much more than their own names. The only one they can rely on is Merry, who, for some reason, hasn't lost her memories. Once they get out of the darkness, they find Alterna destroyed.

First and foremost, what they need is information. Narrowly escaping the town with their lives, they use the skills and abilities their bodies remember to race across the frontier of Grimgar. Then, they meet the forces of the Kingdom of Arabakia, set to take back Alterna?! The tale of adventure born from the ashes enters its end game!