There are two parts to this story, keeping only a focus on only one couple at a time. This is in summer and Kise invited, Kasamatsu, Takao, Midorima [Whom was talked into going by Takao]
First part is Takao and Midorima.

Takao rode the rickshaw to Midorima's house and waited outside for the green haired wonder to come out of his house ready to go. Midorima walked out of his house ready and saw Takao there waiting, and moved towards the rickshaw. "This better be worth my time, Oha-asa said today was for the worst today." He sighed as he got into the back. "But I have my lucky charm." He pulled out a soup in the form of a lotus.
"You need a break Shin-chan." Takao said as he started to ride and get the others.
They picked up Kise and Kasamatsu.
At the end of the day two bikes were added to the rickshaw for Kise, Kasamatsu and Takao to ride. They got to Kises' summer house at around 7pm. He walked in and toured the house for everyone.
Something irritated, Kasamatsu and Midorima was they had to share a bed with the person they didn't want to share a bed with.
"Where's the bath?" Midorima asked Kise.
"Around the corner first door to your right." He smiled at the green haired miracle.
"Ok, well, I am off to have a bath." He took his change of clothes with him and Takao right behind him.
"Takao, what are you doing?" Kuroko asked him as he almost made it past the whole group without noticing.
"Oh, well. I want to join Shin-chan in the bath." He smiled leaving a confused Kise behind.

~Bath time~
Midorima sat in the bath and relaxed with his lotus shaped soup above his head he then heard a click on the door, but he wasn't disturbed by it because he knew who it was. "Why must you come and always take a bath with me Takao?" He asked the raven haired male sternly.
Takao smiled, "If I don't who's going to take care of you?" his smile never leaving his face as he stripped.
Midorima looked away, and prayed this bath will be quickly done with. "I can take care of myself. I am 16 years old now." As slight irritation hung in the air around him.
Takao got in and sat in front of his partner, "But I want to take care of Shin-chan." he spoke as Midorima grabbed the lotus shaped soup and began to scrub Takao's back.
Takao then felt lips on his neck placing small kisses on his shoulder and then nibbled lightly. He gasped and jumped forward away from Midorima as a blush formed on his cheek. He saw Midorima used his lucky item for that day, "Your lotus shaped soup." he exclaimed to the one holding it.
"It's the end of the day Takao. So, it's no use to me any more. Why not put it to good use?" He explained why he used it.
Takao thought and sighed as he turned back around to allow the other to wash his back.
Midorima took his time but couldn't resist the urge to kiss his partners neck. He kissed it and nibbled and wrapped his arms around his victims' waist and held him there.
Takao felt the kiss again on his neck but Midorima wasn't going to let him escape as he had a tight hold on his waist. He bit his lip as he tried to hide the moans trying to escape and his head turned to the side instinctively, without his consent, and let Midorima have more of his neck.
Midorima nibbled up his neck and to his face as he made the other turn his face to look at him. His member twitched at the sight of Takao, all wound up and undone right in front of him.
Takao's face was flushed and his breathing has gotten faster and deeper and turned his head to face him.
Midorima moved his face forward and kissed the one under him with passion as he kissed back with the same amount. He moved his hands up from Takao's waist to his chest and found the already erect nipples then started to tweak and tease them. "I know you want to take care of me, but you take time away from taking care of yourself." he spoke into Takao's ear and nibbled it lightly.
Takao moaned and shivered, "B-but that time I take away from myself, you make it up for me."
Midorima put Takao on his lap and rubbed both their erect members together and groaned lightly as he bit down on Takao's neck making a mark of ownership. His hands roamed down Takao's side and around to his back then over his tender ass. A moan escaped Takao's lips as his hands snaked into Midorima's hair and steals another kiss from the man under him.
Midorima kissed back as he bit the others bottom lip and propped a finger at Takao's entrance and slid it in. He felt the man tense because of the intrusion but soon relaxed when he started to move.
Takao couldn't help but moan into Midorima's mouth as he started to move the intruding finger.
Midorima broke the kiss and looked at Takao as he inserted another finger into him. He thought Takao looked sexy in this position trying to hide his face.
Takao noticed Midorima's stare at him and blushed madly as he thought he looked embarrassing in the position he was in and tried to hide himself.
Midorima smirked and added a third finger seeing the discomfort in his partners face as he scissors and thrust his three fingers but soon the man started to moan as soon as he found the small bundle of nerves.
Takao threw his head back and moaned louder as Midorima hit his prostate again and again with his fingers. He bit his lips as he remembered they weren't the only ones in the house, "Sh-shin-chan, please, I want you." he said through his closed lips.
Midorima removed his fingers with a disapproval whimper from Takao. He picked Takao up and sat him on the edge of the bath and found a liquid soup as he lubricates himself before he positioned himself at Takao's entrance.
Takao looked at Midorima as he pushed himself slowly in and his face screwed up in pain.
Midorima got all the way in and wiped his tear away with his left hand thumb to show how important he is to him. He kissed the other to try and calm him then when he hummed during the kiss Midorima started to move slowly.
Pain and pleasure mixed together as Midorima started slow and Takao wrapped his arms around Midorima's neck and kissed him back deeply.
Midorima got faster and tried to aim for that spot again and after several attempts he finally found the spot to make Takao scream, well tried to cover his scream, and kept hitting that spot.
Takao tried his hardest to keep himself quiet as Midorima rammed into his g spot. Soon he felt Midorima's hand on his member and started to pump it with the same rhythm as his thrust.
Midorima's thrust became harder and faster as he pumped Takao and with his left hand he grabbed a hold of Takao's right hand and kissed it.
Takao bit down hard on his loud moan as he came onto both he and Midorima.
Midorima felt Takao tighten around him and with a low groan came into Takao. He pulled out of Takao and kissed him softly, "You're important to me. You always have been." he then stood and cleaned himself getting changed with Takao right behind him. When they left the bath everyone has already eaten dinner.

So, they had a romantic dinner date after bath sex! Next is KisexKasamutsu!