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Not only I had improved to Tier 1 Rank 5 in a flash, but I had a total of a bit over 500 Spiritual Runes, the power of these Runes were so strong it made it so spirits from our surroundings started swarming me, mostly curiously. They were way smaller and weaker than Arcadia's spirits, but as the days went by, I noticed more and more spirits appearing everywhere.
Maybe as the world slowly absorbs and gets used to Mana, more Spirits are naturally born, and, as an effect of their existence, magical powers, effects, creatures, and more also are strengthened. It could be said that its something similar to the past of Earth when algae completely changed the planet's atmosphere by filling it with Oxygen.
Check "The Protagnist's Sister Is Actually the Strongest"!