Eren had lost.
However, he had lost with grace. He could have made the battle more interesting by keeping on stacking the spells at the cost of burdening his mana circuits. But he chose not to. Because such an expenditure of mana would have raised suspicions even if he had a mana imprint.
'How can a broke ranker like him afford to spend mana potions casually on himself for a test match?' Questions like these getting raised in his onlookers' heads weren't something he wanted.
'My weapon arts. I need mana-points-based weapon art I can use along with Jeet Kune Do.'
Eren also started to realize his shortcomings after fighting with a ranker like Miranda. He was used to fighting with Reece in their spare time. But she's always pulling her punches, never allowing him to take the fight seriously.
