Due to the normal scarcity of elemental crystal mines, and the fact that the 'Omni-Element' elemental crystals were already a mythical existence that was even more scarce, logical thinking could easily prove that these elemental crystals couldn't have been obtained from natural elemental crystal mines…
As such, logically thinking, the only way I would obtain this collection of elemental crystals would be either by someone leaving them for me, or my finding them by chance as some sort of an inheritance, though the amount was just too little for an inheritance, which fit in a good way with my 'Allowance' explanation.
"One hundred one grade 1 elemental crystals plus ten grade 2 elemental crystals…"
"Yup."
"You sure love to surprise us more, young guest…"