"Jun-Boy"
Did they translate the freaking honourific? And use a literal translation?
I mean, I have no problem with some honourifics being translated, so long as they make sense and are actually translated into proper equivalents (Translating "-san" to "Mr." or "Mrs.", "-sama" to "Sir" or "Ma'am", etc.)
"-kun" is one of those ones that shouldn't be translated. You should either leave it in Japanese or just remove it completely, because there isn't really a proper English equivalent.
And yes, in some cases, having someone refer to a younger male as "name boy" is done in English, but it doesn't have a hyphen, is almost always written as "that first or last name boy", and is used to indicate that the speaker isn't all that familiar with the person they are talking about (which isn't the case as Jun is extremely close to Tomo's family), meaning it isn't a proper equivalent. In fact, it's almost the opposite of "-kun", since kun is often used when referring to a male the speaker has known for a long time, or is close with.