They were together.
Haru was the one that made the decision. He never asked him out, or even said they were together, but he showed him.
It was after swim practice when he first showed Mako they were together. They waved goodbye to Rei and Nagisa, and bid farewell to Kou. They were walking to their homes and when they parted, Haru said goodbye with a kiss. Mako was surprised, but he didn't say anything. He simply kissed back.
It became a regular thing for Haru to kiss him goodbye, and Mako learned to expect it. It was always so sudden, and every time he found himself as surprised as the first time. It would either be right when he turned around, or as he opened his mouth to talk, but each time was different, and although he expected it to happen, he never knew what to expect.
At first it would only be when no one else was around, but the unexpectedness got even more bittersweet when Haru kissed him in the pool during swim practice, right in front of all their teammates. They acted as Mako did at first, taken back and silent, but as soon as the sweet-and-short kiss ended and their realization settled in, the pool water began to stir and boil.
Nagisa jumped onto Harus back, pouting his lips and puffing out his cheeks, whining about how Haru hadn't told him. Rei blushed and covered his face mumbling about how even without using calculations he should've known this would happen. Kou and Ama-Chan simply shared a smile as they watched the ruckus in the pool.
When Rin found out he tried to hide how started he was. It was obvious to nearly everyone that he was jealous. Mako had even apologized to Rin, saying he had no idea how it even happened. However this was partly a lie, it was also partly true. Mako didn't know how it happened, and what snapped into Haru to make him kiss him the first night, or any other day, actually. Rin just blushed and turned away, saying he had no idea why he was apologizing, and then he started mumbling about how it was okay because he never had dibs on him. Mako simply smiled at him, feeling slightly guilty. Although he was right. Neither one of them ever had dibs on the boy. Haru just happened to chose him.
After the kiss in the pool they had been together; The kisses became more public and less expected, and they would go places together. Haru would even grab his hand on occasion. Mako would go to Haru's house and he would cook fish for the both of them, or they'd go to Mako's house where they would play videogames, or let the twins fight over who got Haru for themselves. Most times he would even stay for dinner. Sometimes they went on walks, or went to the beach. A lot of the time they were just hanging out at swim practice, having their teammates gawk at them while Nagisa begged them to kiss for him. Nagisa would often ask Rei why they didn't act cute like Haru and Mako, which would cause Rei to panic and rant about how they weren't together like them. Mako would glance at Haru to see his reaction at the mention of them being together, but his expression stayed expressionless.
One day in the middle of Summer, they were taking a walk when another second-year from their school spotted them and walked their way. He asked if they were together and Mako looked to Haru for an answer. Haru simply stared away. The second-year left, hands raised in the air, saying how he understood the situation. How could he, though, when even Mako didn't understand it yet?
One night they were laying in the grass watching the stars when Haru linked their fingers together. Mako swallowed the nervous lump in his throat and asked Haru what he meant to him. Haru sat up and Mako followed. He turned his head and stared into Mako's eyes for a while before answering his question with a long, gentle kiss.
One day when Haru was at Mako's house for dinner, he held his hand under the table. Mako's younger brother noticed, and announced it to everybody at the table. Much to Mako's embarrassment, Haru kept holding his hand with his left, and eating with right. He ignored the younger girl who looked under the table, and the parents who scolded her. He ignored them all and squeezed their hands tighter together.
When it was over and Haru was leaving, Mako met him outside to apologize. Haru said he didn't mind, and gave him a lingering kiss goodbye. When Haru broke the kiss, they both noticed his younger siblings standing on the porch, watching them. Mako's face turned red because he was more embarrassed then he was at dinner, but the twins seemed as neutral as Haru.
The boy asked if they were married, and the girl corrected him by pointing out that they would've had rings if they were married.
Haru squatted down to their height.
"No, we're not married yet." He told them.
When the girl asked if they were together, Haru flatly said yes. He stood up and turned to walk home.
Since that day, whenever someone asked of their relationship, Haru had been the one to answer.
They were together.
And they lived happily ever after that way.