
Is that yumi?? The manager that shuuna called?

Yup the manager guy is yumi but The guy who said manager is not shuuna... tanaka likes to shows that yumi is in osaka. Because he talks in kansai dialect which is a dialect in osaka, where shuna will be transferred.
Sooo... There is a high chance that yumi (ex) and shuuna (present lover) will cross paths.

What just happened? Is this chapter.just a teaser or something? Waaah! But i really like the uke's personality. Hahaha

I'm guessing you skipped this page? http://www.mangago.zone/read-manga/koakuma_baby/nbt/2a54020f4c075abd/Vol1_Ch1/27/
They are both emotionally damaged! They meed to console each other but how!??? Whew!
I'm not sure if 2 emotionally broken people can heal each other...in any case: one of them needs to be stronger than the other, they can switch the roles throughout the healing process from time to time...but if they both fall between the cracks at the same time, the whole construct will collapse.
well....
sometimes it works...sometimes it doesn't...
...however, it's often the case that two people with similiar emotional wounds find each other...or else, "are drawn" to each other.
they will probably be more drawn to each other. they are both longing for love. love that was lost.