While taking their usual bath, the boys discuss how much Kyotaro is like an old man. The next day, when they go to school, they find themselves exhausted by climbing up the stairs... and learn that they're all becoming old men!
In other words, you'll be caring 
for him your whole life.
بعبارة أخرى، ستعتني به طوال حياتك
Das heißt dann also,
dass du ihn ein Leben lang am Hals hast.
Es decir, que lo cuidarás toda la vida.
Es decir, que lo cuidarás toda la vida.
Tu le surveilleras donc à vie.
In altre parole,
ti prenderai cura di lui per il resto della vita.
Em outras palavras, você cuidará
dele pelo resto da sua vida.
То есть ты станешь
его нянькой на всю жизнь.