Reasons

The previous day.

"Fenrir, Anubis, Nidhogg. I need you to sign these contracts."

Nathan presented them with the same contract.

'For 10 Ena, Fenrir will lend the strength enhancement ability for 30 minutes to Nathan. This contract will only be active the moment Nathan wakes up.'

"This is…" Fenrir looked surprised. "The contract looks weird. What does it mean that it will only be active once you wake up?"

"Literally." Nathan smiled. "After upgrading my contract, I have come to realize that the way I word my contract matters a lot. In fact, this is inspired by that one instance when the three of us signed the contract at the same time.