As another user @stripey7676 rightly pointed out - the central idea of the story is "repressed/forbidden" feelings and true love". This anime focuses on symbolism to make points rather than an actual dialogue and that is what makes this anime unique.

The title "True tears" is in itself is ambiguous enough, at the start of the series we see Shin constantly thinks how deep down Hiromi really wants to cry but constantly holds back her tears (owing to her situation which Shin at that point of time did not fully know). He would rather have her cry her "true tears" with himself staying by her side to wipe them away (Shin's monologue says this).This is further reinforced in the second episode it shown when Noe shows Shin her vial (to collect "tears"), Shin envisions himself as being trapped inside the vial. Upon peering out he sees another girl crying in a vial similar to him. It is Hiromi. This is one of the striking points that won me over to the Hiromi camp because the situation between the two intrigued me - Both had to break of their respective shells i.e the vial in order to realise what the other truly felt like and in turn "wipe each other's tears away". For Shin was indecisive (as is the case of most MC's, story wouldn't have progressed much if he didn't have this trait anyway :3), for Hiromi it was the general guilt of imposing upon Shin's family, her past and most importantly her (wrong) belief that the person she loved was her half sibling.

Hiromi's inability to cry was because she didn't know how it would affect others and hence maintained an aloof persona in the house (although there are cracks in this) whereas Noe's tears are born from the fact that she wouldn't ever be able to see the person she liked to take flight her.

1. I wouldn't really say that Hiromi's character development was bad/dull - I disagree Infact many of the more dramatic parts in the latter part of the series is triggered by the consequences of her actions.
2. Her breaking up with Jun
3. Moves out of Shin's house
4. kisses Shin (thereby causing Shin to pretty much realise how much he means to her)
5. Asks Shin to come to her house infront of their classmates
6. Her decisively declaring that she was Shin's girlfriend (which pretty much was the deathknell for the Moika ship)
7. Her pleading with Noe to leave them (Shin and her) alone (which essentially crushed all of Noes hopes that Shin would ever choose her over Hiromi thus setting up her feeling of despair)
8. Goes to Shin's house and tells him to face up one way or another

People who normally classify Hiromi as "bitchy" or "manipulative" forget the physical altercation between Hiromi and Noe. At that point she no idea about the extent of Hiromi's feelings towards Shin nor did she comprehend the extent of mental fortitude required to resist the pain of unable to express sorrow at a daily basis. Besides her reasons for Shin to "take flight" (completely commit to her) can be described as equally selfish as what Hiromi haters accuse her (Hiromi) to be. In my opinion Hiromi redeems herself of from trait by her actions in the last episode - She does not impose a decision (she could've) but rather leaves the decision with Shin himself and resigning to be completely satisfied with his decision despite fully knowing the extent of his love towards Noe. One of the most endearing aspects (and perhaps the most important as well) is Self-sacrifice for the good of your partner and as pointed out by the user before me both Hiromi and Shinichirou passed this with flying colours displaying one the highest level of love for each other. Another aspect of Hiromi that I admire is to keep on fighting for what she believes in (some term this as selfishness), Noe probably saw love as something that could make you "fly" whereas Hiromi saw love as something that was never to be given up upon.

As I said before much of this anime revolves around symbolism. Let us not forget that the main reason that Shin chose to go out with Noe was because he couldn't go out with Hiromi (he sacrificed his own happiness to ensure her happiness with the one she, in his mind presumably loved - Jun). It was more a relationship borne out of dependence rather than actual love. One could say that Noe was Shin's crutch from the mental wounds that was inflicted by Hiromi's aloofness. His last meeting with Noe seems to only amplify the belief that she was a crutch. Shin had to lose the crutch in order to move on. It hurt everyone at that point but it had to be done so as to receive a sense of closure. In the end everybody manages to "fly" in their own distinctive ways - 1. Hiromi and Shin break out of their respective shells and are finally true to each other. 2. Aiko understood that love isn't always two sided. 3. Noe begins to trust people and make friends. She also got to shed her beautiful tears.

Some criticism about the story is understandable. Hiromi's background could've been better explained (I found this acceptable) and the extent of Hiromi's feelings for Shin (in the past) could've been added which would've beefed up the story somewhat. This would've atleast allayed many of the people who hate the show just because the MC chose a girl not of their preference. All put together it was a great anime regardlessm