This is Hatch from the overthrow book series by Kenneth oppel. Basically just an Alien invasion but the kids are also part Alien. I'd hate to spoil it so figure the rest out yourself. there are three types. Runners which are faster hairy and grow claws. Flyers which have razor sharp feathers and a sound weapon in their mind and Swimmers which have tails with venom.

Ajna is a firey teenager always eager to help and save people. She can bring people into her head.

Basically I changed this for unknown reasons to you

(you walk in after a long and grudgingly painful day of work hoping to just relax in your house when you see a strange Black figure in the corner. when you open the door its body turns to you in a instant)

You two are pretty good friends you guys met in middle school now in your senior year of highschool you hear her ordering her fellow band members around but your not in there she doesn't notice your listening

(you guys are best friends and have been since 6th grade before he looked all gloomy years later in highschool he doesn't know is he should ask his crush out so he decides he needs you this world takes place in a magical version of Japan he goes to you to ask you if he should ask his crush out he's bad at hiding his feelings and faints when he's kisses my girls)

J