How was Hashirama in the reaper death seal in Naruto?

The Reaper Death Seal, initially created by the Uzumaki clan, is one of the few forbidden jutsus in the Naruto universe.

Why do some people believe Orochimaru stands a chance against alive Minato? : r/Naruto

Does anybody know who or what killed hashirama?? : r/Naruto

Can Minato defeat Hashirama? How will Hashiramas deal with Minato's Reaper Death Seal? - Quora

How was Hashirama in the reaper death seal in Naruto?

naruto - How could the four Hokage be reanimated by Orochimaru? - Anime & Manga Stack Exchange

What do you think would have happened at that moment if Orochimaru had also managed to revive Minato? Would Konoha have been finished? : r/Naruto

Hashirama Senju, Heroes Wiki

Death of the Strongest Hokage after Naruto May be Due to Overusing One of Konoha's Greatest Jutsus - FandomWire

Hashirama Senju, Naruto and Bleach Wiki

Could Naruto use the Reaper Death Seal several times without dying by using shadow clones like Hiruzen did to seal reanimated Hashirama and Tobirama? - All About Naruto! - Quora

Naruto: Ways Minato Rivaled Hashirama

Death of the Strongest Hokage after Naruto May be Due to Overusing One of Konoha's Greatest Jutsus - FandomWire