As the name suggests, it enhances the effectiveness of the function of, apparently, any ability that the player replicates, even magic, which even Usamimi finds surprising. It was given by Usamimi to follow the player, who was still inexperienced with their ability.
The Boosters give status bonuses depending on the power status that each card has in the game. The three basic types of Boosters are the Normal, Science, and Magic Boosters. Normal Boosters does not give an increase or decrease in status. Science Boosters have a high affinity to espers, and strengthens science side cards and weakens magic side cards. Likewise, the Magic Boosters have a high affinity to magicians, and strengthens magic side cards and weakens science side cards. Apparently, all Boosters apart from the Normal have the capability in growing in strength.
Other Boosters also exist, though they can only be obtained in special events in the game.
Types of Boosters
- Normal Booster (ノーマルブースター Nōmaru Būsutā?) - It is the first Booster the player gets. From the start the Normal Booster is maxed out when the player gets it, as such, its value doesn't grow. Both magic and science cards' numeric values does not increase or decrease when used.
- Science Booster (科学ブースター Kagaku Būsutā?) - It is a Booster that gives positive effects to science side cards, and gives negative effects to magic side cards. When used the width of the increase and decrease value indicator grows.
- Magic Booster (魔術ブースター Majutsu Būsutā?) - Does the complete opposite of the Science Booster. The effects on the increase and decrease value indicator is the same for the Science Booster.
- Protect Booster (プロテクトブースター Purotekuto Būsutā?) - It is a special Booster that is one of the achievement rewards for the Fallen Angel Fuse Kazakiri event in the game. When used it is a Booster that mitigates wide area magic. The Booster is used by Vento of the Front the event boss, and for her alone, the Booster has the effect of giving from the initial value a 10%+ correction to all cards.Furthermore, as a reference, the initial correction value of magic and science cards is 3%.
- Assault Booster (アサルトブースター Asaruto Būsutā?) - A special Booster that is one of the achievement rewards for the Fallen Angel Fuse Kazakiri event in the game. It is a Booster that has been developed for the heavy weapons industry. Against Kihara Amata the positive correction value gets taken.
- Another Booster (アナザーブースター Anaza Būsutā?) - A special Booster that is one of the achievement rewards for the AIM Clone (
幻想擬体?) event in the game. It is a next generation more compact booster. Against AIM Clone the positive correction value gets taken.
- Million Booster (ミリオンブースター Miriombu Būsutā?) - A special Booster that is one of the achievement rewards for the "Visitors From Another World" (「異世界からの来訪者」?) event in the game. It is a next generation more compact booster. It is a homage to the smartphone game Kaku-San-Sei Million Arthur (拡散性ミリオンアーサー?) which Kamachi Kazuma wrote the story for. Against Arthur positive correction value gets taken.
- Boosters from the Toaru Majutsu no Index @wiki (Japanese). Retrieved on 13/1/15