He's bringing out the hand axe anyway, just for this instance. A small axe indeed, only meant for throwing, but still with a good blade on the end. Easy to move, and Tidus gives it a light swing in front of himself; not extended out, so Wangji doesn't have to worry.

"This should be enough. I just need a weapon to strike the person with, see." Here, he gives an even looser swing as an example. "When you use it, it can make even armour or really tough fiends lose their defence! It weakens them - armoury, body..."

And he said a key thing there, didn't he? Feeling more confident as he realises it too.

"If it works on armour, then it should work on a tree trunk! I just need to remember how the spell goes... you need a swing that can shatter even rock itself..."

He's mumbling some to himself, taking a step backwards as he closes his eyes, attempting to remember. The blade and handle starts to glow, and he's now eyeing the tree.

"Take a step back - just in case."