Tetsuo has offered to work with the girls to figure out how Hikari and Yuki, who don't handle heat or sunlight well, can spend summer in comfort. But the school's head teacher suggests that the demi girls' total reliance on Tetsuo might actually be hurting them in the long run. This weighs on Tetsuo's mind...
be the key to learning something 
that could change the world.
.أن يكون مفتاح معرفة شيء قد يغيّر العالم
de ser a chave para descobrir 
uma coisa que mudaria o mundo.
он найдёт ключ к каким-либо
перемена в этом мире.