Saisoku Musou no B-kyuu Mahou Tsukai: Ippatsu Utareru Mae ni Senpatsu Uchikaesu!

In a world where the size of your mana pool decides your standing, Sky, who only had a meager mana pool of five, is branded a failure by his family, despite his noble lineage. However, one day he met a mysterious mage named Ans who imparted his unconventional wisdom onto him. He told him that true strength didn't come from how much mana you had to cast spells, but rather how fast you could fire those spells. What's more, when it came to speed, Sky was a natural. And so, the dropout mage, Sky, began his journey to make a big comeback! (Source: Manga UP!)