Finally, the day of  their debut came. On June 07, 2012 at M! Countdown:

"Now, on their debut stage, with their debut single entitled "Your Only Angel", here's Cheonsa!~ :3

(Singing in unison:)

내가 너만의 천사야, 오빠 제발 사랑해줘요. 영원도록 널 사랑할게, 약속해요

그 누구보다 너만을 위해 내맘이 줄게, 너만을 위해.

(I'm your only angel, please love me. until forever you're the one i'll love, I promise.

I'll give my heart to no one else, but you, only you.)

The dancing part gets more climactic , but strangely, one member sat out.

After their debut performance:

'What happened eonni?', Ri-Soo, Min-Joo and Ye-Jung ask in unison.

'Oh, it's nothing, swear.', Seung-Mi weakly answers.

'Is there a problem? You can tell us.', Hee-Young tries to console Seung-Mi who looked so pale and exhausted.

(Flashback)

4 days before their debut, the management of Cheonsa!~ :3 made the members go through a general medical check-up.

They got their results a day before their set debut date.

Everyone seemed fine at first, but when the management informed Seung-Mi of her results, it devastated her so much that she wasn't able to sleep soundly later in the night.

'Miss Kang Seung-Mi, it seems that we have a problem concerning your health.', the manager tells her.

'Is it a cold? a fever? I can still perform tomorrow if that's the case. No sickness can hinder me from debuting.', she sternly throws an answer.

'We're afraid, it's a lot more serious than you think.'

'Huh? What could it be?', her anxiety grew as she asks what it might be.

'Well...to tell you the truth, we were also startled when your results came out. and we're so sad that you cannot debut with the rest of your group members, dear. You have inherited leukemia from one of your parents' genes. We do hope that you can get cured, but, it doesn't seem that your illness will allow you to continue your activities in Cheonsa!~ :3, so we'll give you a couple of days to tell your fellow members about this.'

'..........', Seung-Mi was baffled and caught in a deafening silence that no one could bear to stand a minute of. seconds later, she broke down in tears.

Her management was totally sad of letting her go, considering that she had the most character and charm in the group.

A thousandfolds sadder, Seung-Mi couldn't think of a way to break the news to her fellow members, who already grew close to her in their years as trainees.

'Eonni....', Seung-Mi's tears start to flow down her cheeks as she opens up to Hee-Young.

'Why!? did someone hurt you? We'll take care of whoever that is for you.', Hee-Young quickly tries to defend her member.

'No, it's not someone. Something's hurting me. My body, my life, everything.'

'Huh? I don't understand. What exactly are you trying to tell me?'

'I'm sick, eonni. I have leukemia. And I was dropped and not allowed to debut with you. In fact, I don't think I'll ever get to be with all of you again.'

The other members were in shock upon hearing the news and a sea of tears came rushing.

'Eonni, don't leave us. were not a team if you won't be with us.', the younger members sob.

'I'm sure I'll get better soon, it's just that, now isn't the right time. I guess.', Seung-Mi clasps her hands tighter  together with Ye-Jung's.

Seung-Mi, then, left with a bitter smile on her face.

And as she walks away farther and farther from her friends, the younger members weren't able to stop their tears from falling down. They became too attached with one another that leaving was too painful for them to take.

'Now, now. She'll be fine. We'll just have to take it as it is. As much as we want her to be with us longer, her condition doesn't permit that to happen. Please, let's stay strong, not only for us, but for Seung-Mi. She won't like it if we get sad because of her. She'll be happier if we make it.', Hee-Young pats the head of the 3 maknaes gently and lets them rest their teary-eyed faces on her shoulders.

What will happen to the future of Cheonsa!~ :3 now that Seung-Mi's left? 

Well, it certainly isn't the end of the road for Cheonsa!~ :3 yet. And surely, no more sad stories will be coming up any soon.

Please anticipate the coming chapters. Thanks. :D